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Encyclopedia > Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. In biochemistry, this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent.[1] In the alpha amino acids, the amino and carboxylate groups are attached to the same carbon, which is called the α–carbon. The various alpha amino acids differ in which side chain (R group) is attached to their alpha carbon. They can vary in size from just a hydrogen atom in glycine through a methyl group in alanine to a large heterocyclic group in tryptophan. It has been suggested that this article or section be merged with Proteinogenic amino acid. ... Image File history File links Phenylalanin_-_Phenylalanine. ... Image File history File links Phenylalanin_-_Phenylalanine. ... Phenyl alanine is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5. ... It has been suggested that this article or section be merged with Proteinogenic amino acid. ... For other uses, see Chemistry (disambiguation). ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... A carboxyl or carboxylic group is a functional group consisting of a carbon atom and an oxygen atom doubly bonded to each other. ... In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules. ... Wöhler observes the synthesis of urea. ... For other uses, see Carbon (disambiguation). ... The Alpha carbon refers to the first carbon after the carbon that attaches to the functional group. ... The term Side chain can have different meanings depending on the context: In chemistry and biochemistry a side chain is a part of a molecule attached to a core structure. ... For the plant, see Glycine (plant). ... Methyl group In chemistry, a methyl group is a hydrophobic alkyl functional group derived from methane (CH4). ... Alanine (Ala, A) also 2-aminopropanoic acid is a non-essential α-amino acid. ... Heterocycles are organic chemical structures containing non-carbon elements. ... Tryptophan (abbreviated as Trp or W)[1] is one of the 20 standard amino acids, which are the building blocks of proteins, and an essential amino acid in the human diet. ...


Beyond the amino acids that are found in all forms of life, many non-natural amino acids have vital roles in technology and industry. For example, the chelating agents EDTA and nitrilotriacetic acid are alpha amino acids that are important in the chemical industry. This article is about life in general. ... Chelation (from Greek, claw like) describes the reversible binding of an organic ligand, the chelator or chelating agent, to a metal ion, forming a metal complex, the chelate. ... EDTA is a widely-used acronym for the chemical compound ethylenediamine tetraacetic acid (and many other names, see table). ... NTA is the chemical compound nitrilotriacetic acid. ... The chemical industry comprises the companies that produce industrial chemicals. ...

Contents

Overview

Alpha-amino acids are the building blocks of proteins. Amino acids combine in a condensation reaction that releases water and the new "amino acid residue" that is held together by a peptide bond. Proteins are defined by their unique sequence of amino acid residues; this sequence is the primary structure of the protein. Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a vast variety of proteins. A representation of the 3D structure of myoglobin showing coloured alpha helices. ... A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... A protein primary structure is a chain of amino acids. ...


Twenty standard amino acids are used by cells in protein biosynthesis, and these are specified by the general genetic code. These 20 amino acids are biosynthesized from other molecules, but organisms differ in which ones they can synthesize and which ones must be provided in their diet. The ones that cannot be synthesized by an organism are called essential amino acids. It has been suggested that this article or section be merged with Proteinogenic amino acid. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Protein biosynthesis (synthesis) is the process in which cells build proteins. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... Biosynthesis is a phenomenon where chemical compounds are produced from simpler reagents. ... An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet. ...


Functions in proteins

See also: Primary structure and Posttranslational modification
A polypeptide is a chain of amino acids.
A polypeptide is a chain of amino acids.

Amino acids are the basic structural building units of proteins. They form short polymer chains called peptides or longer chains called either polypeptides or proteins. The process of such formation from an mRNA template is known as translation, which is part of protein biosynthesis. Twenty amino acids are encoded by the standard genetic code and are called proteinogenic or standard amino acids. Other amino acids contained in proteins are usually formed by post-translational modification, which is modification after translation in protein synthesis. These modifications are often essential for the function or regulation of a protein; for example, the carboxylation of glutamate allows for better binding of calcium cations, and the hydroxylation of proline is critical for maintaining connective tissues and responding to oxygen starvation. Such modifications can also determine the localization of the protein, e.g., the addition of long hydrophobic groups can cause a protein to bind to a phospholipid membrane. A protein primary structure is a chain of amino acids. ... Posttranslational modification is the chemical modification of a protein after its translation. ... Description: The Primary structure of a Protein is a chain of Amino acids. ... Description: The Primary structure of a Protein is a chain of Amino acids. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... A polymer (from Greek: πολυ, polu, many; and μέρος, meros, part) is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... The interaction of mRNA in a eukaryote cell. ... Translation is the second stage of protein biosynthesis (part of the overall process of gene expression). ... For a non-technical introduction to the topic, see Introduction to Genetics. ... The twenty amino acids that are coded in the standard genetic code are called proteinogenic (protein building). ... It has been suggested that this article or section be merged with Proteinogenic amino acid. ... Posttranslational modification means the chemical modification of a protein after its translation. ... A carboxyl or carboxylic group is a functional group consisting of a carbon atom doubly bonded to an oxygen atom and single-bonded to a hydroxyl (-OH) group. ... Glutamate is the anion of glutamic acid. ... Calcium (Ca2+) plays a vital role in the anatomy, physiology and biochemistry of organisms and of the cell, particularly in signal transduction pathways. ... Hydroxylation is any chemical process that introduces one or more hydroxyl groups (-OH) into a compound (or radical) thereby oxidising it. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... Tropocollagen triple helix. ... Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. ... Phospholipid Two schematic representations of a phospholipid. ...


Non-protein functions

The 20 standard amino acids are either used to synthesize proteins and other biomolecules or oxidized to urea and carbon dioxide as a source of energy.[2] The oxidation pathway starts with the removal of the amino group by a transaminase, the amino group is then fed into the urea cycle. The other product of transamidation is a keto acid that enters the citric acid cycle.[3] Glucogenic amino acids can also be converted into glucose, through gluconeogenesis.[4] Urea is an organic compound with the chemical formula (NH2)2CO. Urea is also known as carbamide, especially in the recommended International Nonproprietary Names (rINN) in use in Europe. ... In biochemistry, a transaminase or an aminotransferase is an enzyme that catalyzes a type of reaction between an amino acid and an α-keto acid. ... The reactions of the urea cycle. ... Pyruvic acid Acetoacetic acid Levulinic acid Keto acids are organic acids containing a ketone functional group and a carboxylic acid group. ... A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis. ... Pyruvic acid Oxaloacetic acid Phosphoenolpyruvate Fructose 1,6-bisphosphate Fructose 6-phosphate Glucose-6-phosphate Glucose Gluconeogenesis is the generation of glucose from non-sugar carbon substrates like pyruvate, lactate, glycerol, and amino acids (primarily alanine and glutamine). ...


Hundreds of types of non-protein amino acids have been found in nature and they have multiple functions in living organisms. Microorganisms and plants can produce uncommon amino acids. In microbes, examples include 2-aminoisobutyric acid and lanthionine, which is a sulfide-bridged alanine dimer. Both these amino acids are both found in peptidic lantibiotics such as alamethicin.[5] While in plants, 1-aminocyclopropane-1-carboxylic acid is a small disubstituted cyclic amino acid that is a key intermediate in the production of the plant hormone ethylene.[6] A cluster of Escherichia coli bacteria magnified 10,000 times. ... 2-Aminoisobutyric acid, or α-aminoisobutyric acid (AIB) or α-methylalanine or 2-methylalanine, is an amino acid with the structural formula is H2N-C(CH3)2-COOH. It is contained in some antibiotics of fungal origin, eg. ... Lanthionine is a non proteinogenic amino acid found in peptides of microbial origin. ... Lantibiotics are polycyclic peptides containing uncommon amino acids like the lanthionine, methyllanthionine, 2-aminoisobutyric acid, and unsaturated amino acids such as dehydroalanine. ... Alamethicin is a peptide antibiotic, produced by trichoderma viride. ... 1-Aminocyclopropane-1-carboxylic acid (ACC) is a disubstituted cyclic amino acid. ... Ethylene (or IUPAC name ethene) is the chemical compound with the formula C2H4. ...


In humans, non-protein amino acids also have important roles, such as the neurotransmitter gamma-aminobutyric acid. Many amino acids are used to synthesize other molecules, for example: Chemical structure of D-aspartic acid, a common amino acid neurotransmitter. ... Gamma-aminobutyric acid (usually abbreviated to GABA) is an inhibitory neurotransmitter found in the nervous systems of widely divergent species. ...

Hydroxyproline, hydroxylysine, and sarcosine are also non-protein amino acids. The thyroid hormones are also alpha-amino acids. Tryptophan (abbreviated as Trp or W)[1] is one of the 20 standard amino acids, which are the building blocks of proteins, and an essential amino acid in the human diet. ... For the professional wrestling stable, see Ravens Nest#Serotonin. ... For the plant, see Glycine (plant). ... A porphyrin is a heterocyclic macrocycle made from 4 pyrrole subunits linked on opposite sides through 4 methine bridges. ... Structure of Heme b A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. ... Arginine (abbreviated as Arg or R)[1] is an α-amino acid. ... R-phrases , , , , S-phrases , , , Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Nitric oxide or Nitrogen monoxide is a chemical compound with chemical formula NO. This gas is an important signaling molecule in the body of... This article or section contains information that has not been verified and thus might not be reliable. ... Some common lipids. ... Ornithine is an amino acid, whose structure is: NH2-CH2-CH2-CH2-CHNH2-COOH Ornithine is one of the products of the action of the enzyme arginase on L-arginine, creating urea. ... This article does not cite its references or sources. ... The polyamines are organic compounds having two or more primary amino groups - such as putrescine, cadaverine, spermidine, and spermine - that are growth factors in both eucaryotic and procaryotic cells. ... Homocysteine is a chemical compound with the formula HSCH2CH2CH(NH2)CO2H. It is a homologue of the naturally-occurring amino acid cysteine, differing in that its side-chain contains an additional methylene (-CH2-) group before the thiol (-SH) group. ... Structure of hydroxyproline 4-Hydroxyproline, or hydroxyproline (C5H9O3N), is an uncommon amino acid, abbreviated as HYP, e. ... Hydroxylysine is an amino acid, C6H14N2O3. ... Sarcosine is N-methyl glycine (H3C-NH-CH2-COOH). ... The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid gland. ...


Some amino acids have even been detected in meteorites, especially in a type known as carbonaceous chondrites.[7] This observation has prompted the suggestion that life may have arrived on earth from an extraterrestrial source. Willamette Meteorite A meteorite is a natural object originating in outer space that survives an impact with the Earths surface without being destroyed. ... Some carbonaceous chondrites. ... For the definition, see Life. ...


General structure

Further information: List of standard amino acids
The general structure of an α-amino acid, with the amino group on the left and the carboxyl group on the right.
The general structure of an α-amino acid, with the amino group on the left and the carboxyl group on the right.

In the structure shown at the right, R represents a side chain specific to each amino acid. The central carbon atom, called Cα, is a chiral central carbon atom (with the exception of glycine) to which the two termini and the R-group are attached. Amino acids are usually classified by the properties of the side chain into four groups. The side chain can make them behave like a weak acid, a weak base, a hydrophile if they are polar, and hydrophobe if they are nonpolar. The chemical structures of the 20 standard amino acids, along with their chemical properties, are catalogued in the list of standard amino acids. It has been suggested that this article or section be merged with Proteinogenic amino acid. ... Image File history File links AminoAcidball. ... Image File history File links AminoAcidball. ... The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... A carboxyl or carboxylic group is a functional group consisting of a carbon atom and an oxygen atom doubly bonded to each other. ... The term Side chain can have different meanings depending on the context: In chemistry and biochemistry a side chain is a part of a molecule attached to a core structure. ... For other uses, see Carbon (disambiguation). ... The term chiral (pronounced ) is used to describe an object which is non-superimposable on its mirror image. ... The phrase chemical property is context-dependent, but generally refers to a materials quality which becomes evident during a chemical reaction; this is, which can only be established by changing a substances chemical identity. ... A weak acid is an acid that does not fully ionize in solution; that is, if the acid was represented by the general formula HA, then in aqueous solution a significant amount of undissolved HA still remains. ... Acids and bases: Acid-base reaction theories pH Self-ionization of water Buffer solutions Systematic naming Electrochemistry Acid-base extraction Acids: Strong acids Weak acids Superacids Lewis acids Mineral acids Organic acids Bases: Strong bases Weak bases Superbases Lewis bases Organic bases edit In chemistry, a weak base is a... The common (Arrhenius) definition of a base is a chemical compound that either donates hydroxide ions or absorbs hydrogen ions when dissolved in water. ... Hydrophile, from the Greek (hydros) water and φιλια (philia) friendship, refers to a physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. ... A commonly-used example of a polar compound is water (H2O). ... Hydrophobe (from the Greek (hydros) water and (phobos) fear) in chemistry refers to the physical property of a molecule that is repelled by water. ... In chemistry, a nonpolar compound is one that does not have concentrations of positive or negative electric charge. ... It has been suggested that this article or section be merged with Proteinogenic amino acid. ...


The phrase "branched-chain amino acids" or BCAA is sometimes used to refer to the amino acids having aliphatic side chains that are non-linear; these are leucine, isoleucine, and valine. Proline is the only proteinogenic amino acid whose side group links to the α-amino group and, thus, is also the only proteinogenic amino acid containing a secondary amine at this position. Proline has sometimes been termed an imino acid, but this is not correct in the current nomenclature.[8] In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... In chemistry, non-aromatic and non-cyclic (acyclic) organic compounds are called aliphatic. ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... Isoleucine is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)CH2CH3. ... Valine is an amino acid that cannot be synthesized by humans, so it is considered an essential amino acid for human life. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... The twenty amino acids that are coded in the standard genetic code are called proteinogenic (protein building). ... In chemistry, an imino acid is any molecule that contains both imino (>C=NH) and carboxyl (-C(=O)-OH) functional groups. ...

The two optical isomers of alanine.

Image File history File links D+L-Alanine. ... Image File history File links D+L-Alanine. ...

Isomerism

Most amino acids can exist in either of two optical isomers, called D and L. The L-amino acids represent the vast majority of amino acids found in proteins. D-amino acids are found in some proteins produced by exotic sea-dwelling organisms, such as cone snails.[9] They are also abundant components of the peptidoglycan cell walls of bacteria.[10] Optical isomerism is a form of isomerism (specifically stereoisomerism) where the two different isomers are the same in every way except being non-superposable mirror images of each other. ... A representation of the 3D structure of myoglobin showing coloured alpha helices. ... Genera Asprella Chelyconus Conus Floraconus Leptoconus The cone snails or cone shells, sometimes simply known as cones, (family Conidae), are a taxonomic family of medium-sized to large, sophisticated predatory sea snails, marine gastropod mollusks. ... Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of eubacteria. ... Plant cells separated by transparent cell walls. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ...


The L and D conventions for amino acid configuration do not refer to the optical activity of the amino acid itself, but rather to the optical activity of the isomer of glyceraldehyde having the same stereochemistry as the amino acid. S-glyceraldehyde is levorotary, and R-glyceraldehyde is dexterorotary, and so S-amino acids are called L-amino acids even if they are not levorotary, and R-amino acids are likewise called D-amino acids even if they are not dexterorotary. Fischer projection of D-glyceraldehyde Glyceraldehyde is a triose monosaccharide with chemical formula C3H6O3. ...


There are two exceptions to these general rules of amino acid isomerism. Firstly, glycine, where R = H, no isomerism is possible because the alpha-carbon bears two identical groups (hydrogen). Secondly, in cysteine, the L = S and D = R assignment is reversed to L = R and D = S. Cysteine is structured in the same way as the other amino acids but the sulfur atom alters the interpretation of the Cahn-Ingold-Prelog priority rule. For the plant, see Glycine (plant). ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... This article is about the chemical element. ... To meet Wikipedias quality standards, this article may require cleanup. ...


Reactions

As amino acids have both a primary amine group and a primary carboxyl group, these chemicals can undergo most of the reactions associated with these functional groups. These include nucleophilic addition, amide bond formation and imine formation for the amine group and esterification, amide bond formation and decarboxylation for the carboxylic acid group. The multiple side chains of amino acids can also undergo chemical reactions. The types of these reactions are determined by the groups on these side chains and are discussed in the articles dealing with each specific type of amino acid. The general structure of an amine Amines are organic compounds and a type of functional group that contain nitrogen as the key atom. ... A carboxyl or carboxylic group is a functional group consisting of a carbon atom and an oxygen atom doubly bonded to each other. ... In organic chemistry, a nucleophilic addition reaction is an addition reaction where in a chemical compound a pi bond is removed by the creation of two new covalent bonds by the addition of a nucleophile. ... Amide functional group Amides possess a conjugated system spread over the O, C and N atoms, consisting of molecular orbitals occupied by delocalized electrons. ... Alkylimino-de-oxo-bisubstitution in organic chemistry is the organic reaction of carbonyl compounds with amines to imines . ... Esterification is the general name for a chemical reaction in which two chemicals (typically an alcohol and an acid) form an ester as the reaction product. ... Amide functional group Amides possess a conjugated system spread over the O, C and N atoms, consisting of molecular orbitals occupied by delocalized electrons. ... A Decarboxylation is any chemical reaction in which a carboxyl group (-COOH) is split off from a compound as carbon dioxide (CO2). ...


Peptide bond formation

The condensation of two amino acids to form a peptide bond.
The condensation of two amino acids to form a peptide bond.
For more details on this topic, see Peptide bond.

As both the amine and carboxylic acid groups of amino acids can react to form amide bonds, one amino acid molecule can react with another and become joined through an amide linkage. This polymerization of amino acids is what creates proteins. This condensation reaction yields the newly formed peptide bond and a molecule of water. In cells, this reaction does not occur directly; instead the amino acid is first activated by attachment to a transfer RNA molecule through an ester bond. This aminoacyl-tRNA is produced in an ATP-dependent reaction carried out by an aminoacyl tRNA synthetase.[11] This aminoacyl-tRNA is then a substrate for the ribosome, which catalyzes the attack of the amino group of the elongating protein chain on the ester bond.[12] As a result of this mechanism, all proteins made by ribosomes are synthesized starting at their N-terminus and moving towards their C-terminus. Image File history File links Peptidformationball. ... Image File history File links Peptidformationball. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... An example of alkene polymerisation, in which each Styrene monomer units double bond reforms as a single bond with another styrene monomer and forms polystyrene. ... A condensation reaction is a chemical reaction in which two molecules or moieties combine to form one single molecule, together with the loss of a small molecule. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... Transfer RNA Transfer RNA (abbreviated tRNA), first hypothesized by Francis Crick, is a small RNA chain (73-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... For other uses, see Ester (disambiguation). ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... An aminoacyl tRNA synthetase (abbreviated aaRs) is an enzyme that catalyzes the binding of a specific amino acid to a tRNA to form an aminoacyl-tRNA. The synthetase hydrolyzes ATP to bind the appropriate amino acid to the 3 hydroxyl of the tRNA molecule. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ...


However, not all peptide bonds are formed in this way. In a few cases, peptides are synthesized by specific enzymes. For example, the tripeptide glutathione is an essential part of the defenses of cells against oxidative stress. This peptide is synthesized in two steps from free amino acids.[13] In the first step gamma-glutamylcysteine synthetase condenses cysteine and glutamic acid through a peptide bond formed between the side-chain carboxyl of the glutamate (the gamma carbon of this side chain) and the amino group of the cysteine. This dipeptide is then condensed with glycine by glutathione synthetase to form glutathione.[14] Glutathione (GSH) is a tripeptide. ... Gamma-glutamylcysteine synthetase (EC 6. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... Glutamic acid (Glu, E), is the protonated form of glutamate (the anion). ... For the plant, see Glycine (plant). ... Glutathione synthetase (EC 6. ...


In chemistry, peptides are synthesized by a variety of reactions. One of the most used in solid-phase peptide synthesis, which uses the aromatic oxime derivatives of amino acids as activated units. These are added in sequence onto the growing peptide chain, which is attached to a solid resin support.[15] In organic chemistry, peptide synthesis is the creation of peptides, which are organic compounds in which multiple amino acids bind via peptide bonds which are also known as amide bonds. ...


Zwitterions

An amino acid, in its (1) unionized and (2) zwitterionic forms.
An amino acid, in its (1) unionized and (2) zwitterionic forms.

As amino acids have both the active groups of an amine and a carboxylic acid they can be considered both acid and base. At a certain pH known as the isoelectric point, the amine group has a positive charge (is protonated) and the acid group a negative charge (is deprotonated). The exact value is specific to each different amino acid. This ion is known as a zwitterion, which comes from the German word Zwitter meaning "hybrid". A zwitterion can be extracted from the solution as a white crystalline structure with a very high melting point, due to its dipolar nature. Near-neutral physiological pH allows most free amino acids to exist as zwitterions. Image File history File links Amino_acid_zwitterion. ... Image File history File links Amino_acid_zwitterion. ... The isoelectric point (pI) is the pH at which a molecule or surface carries no net electrical charge. ... Protonation is the addition of a proton (H+) to an atom, molecule, or ion. ... Deprotonation is a chemistry term that refers to the removal of a proton (hydrogen ion H+) from a molecule, forming the conjugate base. ... A zwitterion (from German Zwitter — hybrid, hermaphrodite) is a compound with acidic and basic groups in the same molecule. ...


Hydrophilic and hydrophobic amino acids

Depending on the polarity of the side chain, amino acids vary in their hydrophilic or hydrophobic character. These properties are important in protein structure and protein-protein interactions. The importance of the physical properties of the side chains comes from the influence this has on the amino acid residues' interactions with other structures, both within a single protein and between proteins. The distribution of hydrophilic and hydrophobic amino acids determines the tertiary structure of the protein, and their physical location on the outside structure of the proteins influences their quaternary structure. For example, soluble proteins have surfaces rich with polar amino acids like serine and threonine, while integral membrane proteins tend to have outer ring of hydrophobic amino acids that anchors them into the lipid bilayer, and proteins anchored to the membrane have a hydrophobic end that locks into the membrane. Similarly, proteins that have to bind to positively-charged molecules have surfaces rich with negatively charged amino acids like glutamate and aspartate, while proteins binding to negatively-charged molecules have surfaces rich with positively charged chains like lysine and arginine. Recently a new scale of hydrophobicity based on the free energy of hydrophobic association has been proposed.[16] A commonly-used example of a polar compound is water (H2O). ... Hydrophile, from the Greek (hydros) water and φιλια (philia) friendship, refers to a physical property of a molecule that can transiently bond with water (H2O) through hydrogen bonding. ... Hydrophobe (from the Greek (hydros) water and (phobos) fear) in chemistry refers to the physical property of a molecule that is repelled by water. ... Proteins are an important class of biological macromolecules present in all biological organisms, made up of such elements as carbon, hydrogen, nitrogen, oxygen, and sulfur. ... Protein-protein interactions refer to the association of protein molecules and the study of these associations from the perspective of biochemistry, signal transduction and networks. ... In biochemistry and chemistry, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates. ... In biochemistry, many proteins are actually assemblies of more than one protein (polypeptide) molecule, which in the context of the larger assemblage are known as protein subunits. ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Threonine is one of the 20 natural amino acids. ... An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that is permanently attached to the biological membrane. ... In chemistry, hydrophobic or lipophilic species, or hydrophobes, tend to be electrically neutral and nonpolar, and thus prefer other neutral and nonpolar solvents or molecular environments. ... This fluid lipid bilayer cross section is made up entirely of phosphatidylcholine. ...


Hydrophilic and hydrophobic interactions of the proteins do not have to rely only on the sidechains of amino acids themselves. By various posttranslational modifications other chains can be attached to the proteins, forming hydrophobic lipoproteins or hydrophilic glycoproteins. Posttranslational modification is the chemical modification of a protein after its translation. ... A lipoprotein is a biochemical assembly that contains both proteins and lipids. ... N-linked protein glycosylation (N-glycosylation of N-glycans) at Asn residues (Asn-x-Ser/Thr motifs) in glycoproteins[1]. Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to their polypeptide backbones. ...


Table of standard amino acid abbreviations and side chain properties

Amino Acid 3-Letter 1-Letter Side chain polarity Side chain acidity or basicity of neutral species Hydropathy index[17]
Alanine Ala A nonpolar neutral 1.8
Arginine Arg R polar basic (strongly) -4.5
Asparagine Asn N polar neutral -3.5
Aspartic acid Asp D polar acidic -3.5
Cysteine Cys C polar neutral 2.5
Glutamic acid Glu E polar acidic -3.5
Glutamine Gln Q polar neutral -3.5
Glycine Gly G nonpolar neutral -0.4
Histidine His H polar basic (weakly) -3.2
Isoleucine Ile I nonpolar neutral 4.5
Leucine Leu L nonpolar neutral 3.8
Lysine Lys K polar basic -3.9
Methionine Met M nonpolar neutral 1.9
Phenylalanine Phe F nonpolar neutral 2.8
Proline Pro P nonpolar neutral -1.6
Serine Ser S polar neutral -0.8
Threonine Thr T polar neutral -0.7
Tryptophan Trp W nonpolar neutral -0.9
Tyrosine Tyr Y polar neutral -1.3
Valine Val V nonpolar neutral 4.2

In addition to the normal amino acid codes, placeholders were used historically in cases where chemical or crystallographic analysis of a peptide or protein could not completely establish the identity of a certain residue in a structure. The ones they could not resolve between are these pairs of amino-acids: It has been suggested that this article or section be merged with Proteinogenic amino acid. ... The hydropathy index of a protein is a number representing its hydrophilic or hydrophobic properties. ... Alanine (Ala, A) also 2-aminopropanoic acid is a non-essential α-amino acid. ... Arginine (abbreviated as Arg or R)[1] is an α-amino acid. ... For other articles using the abbreviation or acronym asn see ASN. Asparagine is one of the 20 most common natural amino acids on Earth. ... Aspartic acid (abbreviated as Asp or D; Asx or B represent either aspartic acid or asparagine[1] ) is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CO2H. The L-isomer is a protonated varient of one of the 20 proteinogenic amino acids, i. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... Glutamic acid (Glu, E), is the protonated form of glutamate (the anion). ... Glutamine (abbreviated as Gln or Q; Glx or Z represents either glutamine or glutamic acid) is one of the 20 amino acids encoded by the standard genetic code. ... For the plant, see Glycine (plant). ... Histidine is one of the 20 most common natural amino acids present in proteins. ... Isoleucine is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)CH2CH3. ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... Lysine is one of the 20 amino acids normally found in proteins. ... Methionine is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CH2SCH3. ... Phenyl alanine is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Threonine is one of the 20 natural amino acids. ... Tryptophan (abbreviated as Trp or W)[1] is one of the 20 standard amino acids, which are the building blocks of proteins, and an essential amino acid in the human diet. ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Valine is an amino acid that cannot be synthesized by humans, so it is considered an essential amino acid for human life. ... Proteins are found in every cell and are essential to every biological process, protein structure is very complex: determining a proteins structure involves first protein sequencing - determining the amino acid sequences of its constituent peptides; and also determining what conformation it adopts and whether it is complexed with any... X-ray crystallography, also known as single-crystal X-ray diffraction, is the oldest and most common crystallographic method for determining the structure of molecules. ...

Ambiguous Amino Acids 3-Letter 1-Letter
Asparagine or aspartic acid Asx B
Glutamine or glutamic acid Glx Z
Leucine or Isoleucine Xle J
Unspecified or unknown amino acid Xaa X

Unk is sometimes used instead of Xaa, but is less standard.


Nonstandard amino acids

The amino acid selenocysteine.
The amino acid selenocysteine.

Aside from the twenty standard amino acids, there are a vast number of "non-standard" amino acids. Two of these can be specified by the genetic code, but are rather rare in proteins. Selenocysteine is incorporated into some proteins at a UGA codon, which is normally a stop codon.[18] Pyrrolysine is used by some methanogenic archaea in enzymes that they use to produce methane. It is coded for with the codon UAG.[19] Image File history File links Size of this preview: 711 × 600 pixel Image in higher resolution (1100 × 928 pixel, file size: 22 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Amino acid Selenocysteine... Image File history File links Size of this preview: 711 × 600 pixel Image in higher resolution (1100 × 928 pixel, file size: 22 KB, MIME type: image/png) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Amino acid Selenocysteine... Skeletal formula of L-selenocysteine Space-filling model of L-selenocysteine Selenocysteine is an amino acid that is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5 deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases and some hydrogenases). ... Skeletal formula of L-selenocysteine Space-filling model of L-selenocysteine Selenocysteine is an amino acid that is present in several enzymes (for example glutathione peroxidases, tetraiodothyronine 5 deiodinases, thioredoxin reductases, formate dehydrogenases, glycine reductases and some hydrogenases). ... RNA codons. ... Pyrrolysine is a naturally-occurring genetically-coded amino acid. ... Methanogens are archaea that produce methane as a metabolic byproduct in anoxic conditions. ... Phyla Crenarchaeota Euryarchaeota Korarchaeota Nanoarchaeota ARMAN The Archaea (pronounced ) are a group of prokaryotic and single-celled microorganisms. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Methane is a chemical compound with the molecular formula . ...


Examples of nonstandard amino acids that are not found in proteins include lanthionine, 2-aminoisobutyric acid, dehydroalanine and the neurotransmitter gamma-aminobutyric acid. Nonstandard amino acids often occur as intermediates in the metabolic pathways for standard amino acids — for example ornithine and citrulline occur in the urea cycle, part of amino acid catabolism.[20] Lanthionine is a non proteinogenic amino acid found in peptides of microbial origin. ... 2-Aminoisobutyric acid, or α-aminoisobutyric acid (AIB) or α-methylalanine or 2-methylalanine, is an amino acid with the structural formula is H2N-C(CH3)2-COOH. It is contained in some antibiotics of fungal origin, eg. ... Dehydroalanine (or (alpha)-(beta)-di-dehydroalanine) is an uncommon amino acid found in peptides of microbial origin (an unsaturated amino acid). ... Gamma-aminobutyric acid (usually abbreviated to GABA) is an inhibitory neurotransmitter found in the nervous systems of widely divergent species. ... In biochemistry, a metabolic pathway is a series of chemical reactions occurring within a cell. ... Ornithine is an amino acid, whose structure is: NH2-CH2-CH2-CH2-CHNH2-COOH Ornithine is one of the products of the action of the enzyme arginase on L-arginine, creating urea. ... The chemical compound citrulline is an α-amino acid (AA). ... The reactions of the urea cycle. ... Anabolism is the aspect of metabolism that contributes to growth. ...


Nonstandard amino acids are usually formed through modifications to standard amino acids. For example, homocysteine is formed through the transsulfuration pathway or by the demethylation of methionine via the intermediate metabolite S-adenosyl methionine,[21] while dopamine is synthesized from l-DOPA, and hydroxyproline is made by a posttranslational modification of proline.[22] Homocysteine is a chemical compound with the formula HSCH2CH2CH(NH2)CO2H. It is a homologue of the naturally-occurring amino acid cysteine, differing in that its side-chain contains an additional methylene (-CH2-) group before the thiol (-SH) group. ... The transsulfuration pathway is a metabolic pathway that converts cysteine to homocysteine, through the intermediate cystathionine. ... This article does not cite its references or sources. ... Structure of hydroxyproline 4-Hydroxyproline, or hydroxyproline (C5H9O3N), is an uncommon amino acid, abbreviated as HYP, e. ... Posttranslational modification is the chemical modification of a protein after its translation. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ...


Uses in technology

Amino acid derivative Use in industry
Aspartame (aspartyl-phenylalanine-1-methyl ester) Low-calorie artificial sweetener
5-HTP (5-hydroxytryptophan) Treatment for depression and the neurological problems of phenylketonuria.
L-DOPA (L-dihydroxyphenylalanine) Treatment for Parkinsonism.
Monosodium glutamate Food additive that enhances flavor. Confers the taste umami.

Aspartame (or APM) (pronounced or ) is the name for an artificial, non-saccharide sweetener, aspartyl-phenylalanine-1-methyl ester; i. ... A sweetener is a food additive which adds the basic taste of sweetness to a food. ... 5-HTP (5-Hydroxy-tryptophan) is decarboxylated to the neurotransmitter serotonin (5-HT) by the enzyme aromatic-L-amino-acid decarboxylase. ... Phenylketonuria (PKU) is an autosomal recessive genetic disorder characterized by a deficiency in the enzyme phenylalanine hydroxylase (PAH). ... // Therapeutic use L-DOPA is used to replace dopamine lost in Parkinsons disease because dopamine itself cannot cross the blood-brain barrierwhere its precursor can. ... Parkinsonism (also known as Parkinsons syndrome, atypical Parkinsons, or secondary Parkinsons) is a neurological syndrome characterized by tremor, hypokinesia, rigidity, and postural instability. ... This article is about the chemical compound. ... Food additives are substances added to food to preserve flavor or improve its taste and appearance. ... Human taste sensory organs, called taste buds or gustatory calyculi, and concentrated on the upper surface of the tongue, appear to be receptive to relatively few chemical species as tastes. ...

Nutritional importance

Further information: Protein in nutrition

Of the 20 standard proteinogenic amino acids, 8 are called essential amino acids because the human body cannot synthesize them from other compounds at the level needed for normal growth, so they must be obtained from food.[23] However, the situation is a little more complicated since cysteine, tyrosine, histidine and arginine are semiessential amino acids in children, because the metabolic pathways that synthesize these amino acids are not fully developed.[24] The amounts required also depend on the age and health of the individual, so it is hard to make general statements about the dietary requirement for some amino acids. Proteins are broken down in the stomach during digestion by enzymes known as proteases into smaller polypeptides to provide amino acids for the organism, including the essential amino acids that the organism cannot biosynthesize itself. ... An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet. ... Physical Features of the Human Body The human body is the entire physical structure of a human organism. ... Synthesis (from the Greek words syn = plus and thesis = position) is commonly understood to be an integration of two or more pre-existing elements which results in a new creation. ... Look up chemical compound in Wiktionary, the free dictionary. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Histidine is one of the 20 most common natural amino acids present in proteins. ... Arginine (abbreviated as Arg or R)[1] is an α-amino acid. ...

Essential Nonessential
Isoleucine Alanine
Leucine Asparagine
Lysine Aspartate
Methionine Cysteine*
Phenylalanine Glutamate
Threonine Glutamine*
Tryptophan Glycine*
Valine Proline*
Arginine* Serine*
Histidine* Tyrosine*

(*) Essential only in certain cases.[25][26] Isoleucine is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)CH2CH3. ... Alanine (Ala, A) also 2-aminopropanoic acid is a non-essential α-amino acid. ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... For other articles using the abbreviation or acronym asn see ASN. Asparagine is one of the 20 most common natural amino acids on Earth. ... Lysine is one of the 20 amino acids normally found in proteins. ... Aspartic acid, also known as aspartate, the name of its anion, is one of the 20 natural proteinogenic amino acids which are the building blocks of proteins. ... Methionine is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CH2SCH3. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... Phenyl alanine is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5. ... Glutamate is the anion of glutamic acid. ... Threonine is one of the 20 natural amino acids. ... Glutamine (abbreviated as Gln or Q; Glx or Z represents either glutamine or glutamic acid) is one of the 20 amino acids encoded by the standard genetic code. ... Tryptophan (abbreviated as Trp or W)[1] is one of the 20 standard amino acids, which are the building blocks of proteins, and an essential amino acid in the human diet. ... For the plant, see Glycine (plant). ... Valine is an amino acid that cannot be synthesized by humans, so it is considered an essential amino acid for human life. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... Arginine (abbreviated as Arg or R)[1] is an α-amino acid. ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Histidine is one of the 20 most common natural amino acids present in proteins. ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells...


Several common mnemonics have evolved for remembering the ten amino acids often described as essential. PVT TIM HALL ("Private Tim Hall") uses the first letter of each of these amino acids.[27] Another mnemonic that frequently occurs in student practice materials beneath "AH TV TILL Past Midnight", is "These ten valuable amino acids have long preserved life in man".[28] For other uses, see Mnemonic (disambiguation). ... A Private is a soldier of the lowest military rank (equivalent to Nato Rank Grades OR-1 to OR-3 depending on the force served in). ...


See also

Wöhler observes the synthesis of urea. ... Figure 1: β-alanine, an example of a β amino acid. ... The Strecker amino acid synthesis is a series of chemical reactions that synthesize an amino acid from an aldehyde (or ketone). ... A glucogenic amino acid is an amino acid that can be converted into glucose through gluconeogenesis. ... Homochirality is a term used to refer to a group of molecules that possess the same sense of chirality. ... Fragment of the Murchison meteorite (at right) and isolated individual particles (shown in the test tube). ... For a non-technical introduction to the topic, see Introduction to Genetics. ... It has been suggested that this article or section be merged with Proteinogenic amino acid. ... Amino acid dating is a technique used to estimate age in a wide variety of situations. ...

References and notes

  1. ^ Proline is an exception to this general formula. It lacks the NH2 group because of the cyclization of the side chain.
  2. ^ Sakami W, Harrington H. "Amino acid metabolism". Annu Rev Biochem 32: 355-98. PMID 14144484. 
  3. ^ Brosnan J (2000). "Glutamate, at the interface between amino acid and carbohydrate metabolism". J Nutr 130 (4S Suppl): 988S-90S. PMID 10736367. 
  4. ^ Young V, Ajami A (2001). "Glutamine: the emperor or his clothes?". J Nutr 131 (9 Suppl): 2449S-59S; discussion 2486S-7S. PMID 11533293. 
  5. ^ Whitmore L, Wallace B (2004). "Analysis of peptaibol sequence composition: implications for in vivo synthesis and channel formation.". Eur Biophys J 33 (3): 233-7. PMID 14534753. 
  6. ^ Alexander L, Grierson D (2002). "Ethylene biosynthesis and action in tomato: a model for climacteric fruit ripening". J Exp Bot 53 (377): 2039-55. PMID 12324528. 
  7. ^ Llorca J (2004). "Organic matter in meteorites.". Int Microbiol 7 (4): 239-48. PMID 15666244. 
  8. ^ Claude Liebecq (Ed) Biochemical Nomenclature and Related Documents, 2nd edition, Portland Press, 1992, pages 39-69 ISBN 978-1855780057
  9. ^ Pisarewicz K, Mora D, Pflueger F, Fields G, Marí F (2005). "Polypeptide chains containing D-gamma-hydroxyvaline.". J Am Chem Soc 127 (17): 6207-15. PMID 15853325. 
  10. ^ van Heijenoort J (2001). "Formation of the glycan chains in the synthesis of bacterial peptidoglycan.". Glycobiology 11 (3): 25R-36R. PMID 11320055. 
  11. ^ Ibba M, Söll D (2001). "The renaissance of aminoacyl-tRNA synthesis". EMBO Rep 2 (5): 382-7. PMID 11375928. 
  12. ^ Lengyel P, Söll D (1969). "Mechanism of protein biosynthesis". Bacteriol Rev 33 (2): 264-301. PMID 4896351. 
  13. ^ Wu G, Fang Y, Yang S, Lupton J, Turner N (2004). "Glutathione metabolism and its implications for health". J Nutr 134 (3): 489-92. PMID 14988435. 
  14. ^ Meister A (1988). "Glutathione metabolism and its selective modification". J Biol Chem 263 (33): 17205–8. PMID 3053703. 
  15. ^ Carpino, L. A. (1992) 1-Hydroxy-7-azabenzotriazole. An efficient Peptide Coupling Additive. J. Am. Chem. Soc. 115, 4397-4398.
  16. ^ Urry, D. W. (2004). "The change in Gibbs free energy for hydrophobic association - Derivation and evaluation by means of inverse temperature transitions". Chemical Physics Letters 399 (1-3): 177-183. 
  17. ^ Kyte J & RF Doolittle (1982). "A simple method for displaying the hydropathic character of a protein". J. Mol. Biol. (157): 105-132. PMID 7108955. 
  18. ^ Driscoll D, Copeland P. "Mechanism and regulation of selenoprotein synthesis.". Annu Rev Nutr 23: 17-40. PMID 12524431. 
  19. ^ Krzycki J (2005). "The direct genetic encoding of pyrrolysine.". Curr Opin Microbiol 8 (6): 706-12. PMID 16256420. 
  20. ^ Curis E, Nicolis I, Moinard C, Osowska S, Zerrouk N, Bénazeth S, Cynober L (2005). "Almost all about citrulline in mammals". Amino Acids 29 (3): 177-205. PMID 16082501. 
  21. ^ Brosnan J, Brosnan M (2006). "The sulfur-containing amino acids: an overview". J Nutr 136 (6 Suppl): 1636S-1640S. PMID 16702333. 
  22. ^ Kivirikko K, Pihlajaniemi T. "Collagen hydroxylases and the protein disulfide isomerase subunit of prolyl 4-hydroxylases". Adv Enzymol Relat Areas Mol Biol 72: 325-98. PMID 9559057. 
  23. ^ Young VR (1994). "Adult amino acid requirements: the case for a major revision in current recommendations". J. Nutr. 124 (8 Suppl): 1517S–1523S. PMID 8064412. 
  24. ^ Imura K, Okada A (1998). "Amino acid metabolism in pediatric patients". Nutrition 14 (1): 143-8. PMID 9437700. 
  25. ^ Fürst P, Stehle P (2004). "What are the essential elements needed for the determination of amino acid requirements in humans?". J. Nutr. 134 (6 Suppl): 1558S–1565S. PMID 15173430. 
  26. ^ Reeds PJ (2000). "Dispensable and indispensable amino acids for humans". J. Nutr. 130 (7): 1835S–40S. PMID 10867060. 
  27. ^ Chapter 39 PVT TIM HALL. Retrieved on 2007-09-29.
  28. ^ Memory aids for medical biochemistry. http://mednote.co.kr/Yellownote/BIOCHMNEMON.htm Access date 25 February 2006

Year 2007 (MMVII) was a common year starting on Monday of the Gregorian calendar in the 21st century. ... is the 272nd day of the year (273rd in leap years) in the Gregorian calendar. ... is the 56th day of the year in the Gregorian calendar. ... Year 2006 (MMVI) was a common year starting on Sunday of the Gregorian calendar. ...

Further reading

  • Doolittle, R.F. (1989) Redundancies in protein sequences. In Predictions of Protein Structure and the Principles of Protein Conformation (Fasman, G.D. ed) Plenum Press, New York, pp. 599-623
  • David L. Nelson and Michael M. Cox, Lehninger Principles of Biochemistry, 3rd edition, 2000, Worth Publishers, ISBN 1-57259-153-6

External links


Alanine (Ala, A) also 2-aminopropanoic acid is a non-essential α-amino acid. ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  206-418-1 EINECS for D-alanine a  200-273-8 EINECS for L-alanine a  PubChem 602 a  PubChem 5950 This... Arginine (abbreviated as Arg or R)[1] is an α-amino acid. ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  EINECS number 205-866-5 ((-)-D-arginine hydrate) a  EINECS number 200-811-1 (for L-arginine) a  CID 71070 from PubChem... For other articles using the abbreviation or acronym asn see ASN. Asparagine is one of the 20 most common natural amino acids on Earth. ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  CID 6267 from PubChem (L-asparagine) This article is maintained by WP:Chemicals (Talk)  WP:Drugs (Talk)  WP:Molecular and Cellular Biology... Aspartic acid (abbreviated as Asp or D; Asx or B represent either aspartic acid or asparagine[1] ) is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CO2H. The L-isomer is a protonated varient of one of the 20 proteinogenic amino acids, i. ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  CID 424 from PubChem — racemic a  CID 83887 from PubChem — (D-aspartic acid) a  CID 5960 from PubChem — (L-aspartic acid) a... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  [1] This article is maintained by WP:Chemicals (Talk)  WP:Drugs (Talk)  WP:Molecular and Cellular Biology (Talk)   Categories: ... Glutamic acid (Glu, E), is the protonated form of glutamate (the anion). ... Physical properties Hazard properties Flash point - N/A R/S statement R: N/A S: N/A RTECS number: N/A Chemical properties Pharmacological properties OrganicBox_complete References a  CID 23327 from PubChem (D-glutamic acid) a  CID 33032 from PubChem (L-glutamic acid) This article is maintained by WP:Chemicals... Glutamine (abbreviated as Gln or Q; Glx or Z represents either glutamine or glutamic acid) is one of the 20 amino acids encoded by the standard genetic code. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete References a  CID 738 from PubChem (Gln) a  CID 145815 from PubChem (D) a  CID 5961 from PubChem (L) ... For the plant, see Glycine (plant). ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete References a  EINECS number 200-272-2 a  b  c  d  e  CID 750 from PubChem (Glycine) ... Histidine is one of the 20 most common natural amino acids present in proteins. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete References a  EINECS number 200-745-3 (D-histidine) a  EINECS number 206-513-8 (L-histidine) a  CID 71083 from PubChem (D-histidine) a  CID 6274 from PubChem (L-histidine) ... Isoleucine is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)CH2CH3. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete References a  b  c  d  e  f  g  PubChem 6306 ... Leucine is one of the 20 most common amino acids and coded for by DNA. It is isomeric with isoleucine. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete References a  b  c  d  e  PubChem 6106 Categories: | ... Lysine is one of the 20 amino acids normally found in proteins. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  EINECS number 200-294-2 (Lysine) a  CID 866 from PubChem (DL-Lysine) a  CID 5962 from PubChem (L-Lysine) Category: ... Methionine is an α-amino acid with the chemical formula HO2CCH(NH2)CH2CH2SCH3. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  63-68-3 EINECS for L-Methionine a  PubChem 876 a  PubChem 6137 Category: ... Phenyl alanine is an α-amino acid with the formula HO2CCH(NH2)CH2C6H5. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  EINECS number 200-568-1 (phenylalanine) a  CID 994 from PubChem (phenylalanine) a  CID 71567 from PubChem (D-phenylalanine) a  CID 6140 from PubChem (L-phenylalanine) Category: ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  205-702-2 EINECS for Proline a  PubChem 6148988 a  PubChem 6137 Category: ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  200-274-3 EINECS for Serine a  PubChem 617 a  PubChem 5951 Category: ... Threonine is one of the 20 natural amino acids. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  EINECS number 200-774-1 (Threonine) a  CID 69435 from PubChem (D-Threonine) a  CID 6288 from PubChem (L-Threonine) Category: ... Tryptophan (abbreviated as Trp or W)[1] is one of the 20 standard amino acids, which are the building blocks of proteins, and an essential amino acid in the human diet. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  73-22-3 EINECS for Tryptophan a  PubChem 9060 a  PubChem 6305 Category: ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  200-460-4 EINECS for Tyrosine a  PubChem 71098 a  PubChem 1153 Category: ... Valine is an amino acid that cannot be synthesized by humans, so it is considered an essential amino acid for human life. ... Physical properties Hazard properties Chemical properties Pharmacological properties OrganicBox_complete a  200-773-6 EINECS for Valine a  PubChem 71563 a  PubChem 1182 Category: ... Wöhler observes the synthesis of urea. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... Look up nucleic acid in Wiktionary, the free dictionary. ... Lactose is a disaccharide found in milk. ... Nucleotide sugars are biochemicals that act as donors of sugar residues in nucleotide sugars metabolism. ... Some common lipids. ... Many terpenes are derived from conifer resins, here a pine. ... The orange ring surrounding Grand Prismatic Spring is due to carotenoid molecules, produced by huge mats of algae and bacteria. ... Polypyrrole A Polypyrrole (PPy) is a chemical compound formed from a number of connected pyrrole ring structures. ... A cofactor is any substance that needs to be present in addition to an enzyme to catalyze a certain reaction. ... This article is about the chemical family of steroids. ... Molecular structure of the flavone backbone (2-phenyl-1,4-benzopyrone) The term flavonoid refers to a class of plant secondary metabolites. ... Chemical structure of ephedrine, a phenethylamine alkaloid An alkaloid is a nitrogen-containing naturally occurring compound, produced by a large variety of organisms, including fungi, plants, animals, and bacteria. ... Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. ... A glycoside is a molecule where a sugar group is bonded through its anomeric carbon to a nonsugar group by either an oxygen or a nitrogen atom. ... A protein primary structure is a chain of amino acids. ... Posttranslational modification is the chemical modification of a protein after its translation. ... Protein biosynthesis (synthesis) is the process in which cells build proteins. ... A peptide bond is a chemical bond that is formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule, releasing a molecule of water (H2O). ... Proteolysis is the directed degradation (digestion) of proteins by cellular enzymes called proteases or by intramolecular digestion. ... In chemistry racemization refers to partial conversion of one enantiomer into another. ... The N-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free amine group (NH2). ... Acetylation describes a reaction, usually with acetic acid, that introduces an acetyl functional group into an organic compound. ... Categories: | | ... Pyroglutamic acid is an uncommon amino acid found in bacteriorhodopsin. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... Glycation is the result of a sugar-reducing molecule, such as fructose or glucose, bonding to a protein or lipid molecule without the controlling action of an enzyme. ... This article needs to be wikified. ... The C-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free carboxyl group (COOH). ... Amide functional group In chemistry, an amide is one of two kinds of compounds: the organic functional group characterized by a carbonyl group (C=O) linked to a nitrogen atom (N), or a compound that contains this functional group (pictured to the right); or a particular kind of nitrogen anion. ... A GPI anchor or glycosylphosphatidylinositol is a common posttranslational modification of the C-terminus of membrane-attached proteins. ... // Background Ubiquitylation, also termed ubiquitination, refers to the process particular to eukaryotes whereby a protein is post-translationally modified by covalent attachment of a small protein. ... Small Ubiquitin-related Modifier or SUMO proteins are a family of small proteins that are covalently attached to and detached from other proteins in cells to modify their function. ... Lysine is one of the 20 amino acids normally found in proteins. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... Acetylation describes a reaction, usually with acetic acid, that introduces an acetyl functional group into an organic compound. ... In chemistry, acylation is the process of adding an acyl group to a compound. ... Hydroxylation is any chemical process that introduces one or more hydroxyl groups (-OH) into a compound (or radical) thereby oxidising it. ... Ubiquitin is a very conserved small regulatory protein that is ubiquitous in eukaryotes. ... Small Ubiquitin-related Modifier or SUMO proteins are a family of small proteins that are covalently attached to and detached from other proteins in cells to modify their function. ... A desmosine cross-link is formed when three allysyl side chains plus one unaltered lysl side chain from the same or neighbouring polypeptides. ... ADP ribose ADP-ribosylation is a posttranslational modification of proteins that involves the addition of one or more ADP and ribose moieties. ... Deamination is the removal of an amine group from a molecule. ... Oxidative deamination is a form of deamination which generates oxoacids in the liver. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ... Prenylation or isoprenylation is the addition of hydrophobic molecules to a protein to facilitate its attachment to the cell membrane. ... Palmitoylation is the covalent attachment of fatty acids to cysteine residues of membrane proteins [1] ^ Linder, M.E. (2000). ... Serine (IPA ), organic compound, one of the 20 amino acids commonly found in animal proteins. ... Threonine is one of the 20 natural amino acids. ... A phosphorylated serine residue Phosphorylation is the addition of a phosphate (PO4) group to a protein molecule or a small molecule. ... Glycosylation is the process or result of addition of saccharides to proteins and lipids. ... Histidine ammonia-lyase (or histidase) is an enzyme which converts histidine into ammonia and urocanic acid. ... Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese[1][2]), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells... A phosphorylated serine residue Phosphorylation is the addition of a phosphate (PO4) group to a protein molecule or a small molecule. ... Tyrosine sulfation is a posttranslational modification where a sulfate group is added to a tyrosine residue of a protein molecule. ... Structure of porphine, the simplest porphyrin. ... Riboflavin Flavin is a vaginal ring whose biochemical smell is pungent. ... It has been suggested that mGFP be merged into this article or section. ... For other articles using the abbreviation or acronym asn see ASN. Asparagine is one of the 20 most common natural amino acids on Earth. ... Deamidation reaction of Asn-Gly (top right) to Asp-Gly (at left) or iso(Asp)-Gly (in green at bottom right). ... Glycosylation is the process or result of addition of saccharides to proteins and lipids. ... Aspartic acid, also known as aspartate, the name of its anion, is one of the 20 natural proteinogenic amino acids which are the building blocks of proteins. ... Deamidation reaction of Asn-Gly (top right) to Asp-Gly (at left) or iso(Asp)-Gly (in green at bottom right). ... Glutamine (abbreviated as Gln or Q; Glx or Z represents either glutamine or glutamic acid) is one of the 20 amino acids encoded by the standard genetic code. ... Glutamate is the anion of glutamic acid. ... A carboxyl or carboxylic group is a functional group consisting of a carbon atom doubly bonded to an oxygen atom and single-bonded to a hydroxyl (-OH) group. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... A form of reversible posttranslational modification of glutamate residues seen for example in alpha and beta tubulins, nucleosome assembly proteins NAP1 and NAP2. ... Polyglycylation is a form of posttranslational modification of glutamate residues of the carboxyl-terminal region tubulin in certain microtubules (eg axonemal) originally discovered in paramecium[1], and later shown in mammalian neurons as well[2]. ^ Redeker, V., Levilliers, N., Schmitter, J.M., Le Caer, J.P., Rossier, J., Adoutte, A... Arginine (abbreviated as Arg or R)[1] is an α-amino acid. ... Citrullination or deimination is the term used for the post-translational modification of the amino acid arginine in a protein into the amino acid citrulline. ... Methylation is a term used in the chemical sciences to denote the attachment or substitution of a methyl group on various substrates. ... Proline is an α-amino acid with the chemical formula HO2CCH(NH[CH2)3]. L-Proline is one of the twenty DNA-encoded amino acids. ... Hydroxylation is any chemical process that introduces one or more hydroxyl groups (-OH) into a compound (or radical) thereby oxidising it. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... A representation of the 3D structure of the myoglobin protein. ...

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Amino Acids (479 words)
The precise amino acid content, and the sequence of those amino acids, of a specific protein, is determined by the sequence of the bases in the gene that encodes that protein.
The chemical properties of the amino acids of proteins determine the biological activity of the protein.
The essential amino acids are arginine (required for the young, but not for adults), histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Biochemistry of Amino Acids (985 words)
The hydrophobic amino acids tend to repel the aqueous environment and, therefore, reside predominantly in the interior of proteins.
The hydrophilic amino acids tend to interact with the aqeuous environment, are often involved in the formation of H-bonds and are predominantly found on the exterior surfaces proteins or in the reactive centers of enzymes.
Conversely, the hydrophilic amino acids are generally found on the exterior of proteins as well as in the active centers of enzymatically active proteins.
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