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Encyclopedia > Peptide

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. The link between one amino acid residue and the next is an amide bond, and is sometimes referred to as a peptide bond. In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... An amino acid residue is what is left of an amino acid once a molecule of water has been lost (an H+ from the nitrogenous side and an OH- from the carboxylic side) in the formation of a peptide bond. ... Amide functional group In chemistry, an amide is one of two kinds of compound. ... A chemical bond is the physical phenomenon of chemical substances being held together by attraction of atoms to each other through sharing, as well as exchanging, of electrons or electrostatic forces. ... A peptide bond is a chemical bond 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). ...


Proteins are polypeptide molecules. The distinction is that peptides are short and proteins are long. There are several different conventions to determine these, all of which have flaws. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...


One convention is that those peptide chains that are short enough to be made synthetically from the constituent amino acids are called peptides rather than proteins. However with the advent of better synthetic techniques, peptides as long as hundreds of amino acids can be made, including full proteins like ubiquitin. Native chemical ligation has given access to even longer proteins, and so this convention seems to be outdated. An amino acid residue is what is left of an amino acid once a molecule of water has been lost (an H+ from the nitrogenous side and an OH- from the carboxylic side) in the formation of a peptide bond. ... // 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. ... Native chemical ligation is a technique for constructing a large peptide from two smaller peptides, a C-terminal thioester peptide and a N-terminal cysteine peptide. ...


Another convention places an informal dividing line is at approximately 50 amino acids in length (some people claim shorter lengths). However, this definition is somewhat arbitrary — some peptides such as alzheimer's beta peptide can be considered proteins and some proteins (such as insulin) are close to the upper limit for peptides. Because of the arbitrary nature of this definition, there is considerable movement within the scientific community to ascribe the more-specific definition that "a peptide is an amino acid molecule without secondary structure; on gaining defined structure, it is a protein." Thus the same molecule can be either a peptide or a protein depending on its environment, though there are peptides that cannot be proteins. Amyloid beta (Aβ or Abeta) is a protein fragment of 39-42 amino acids that is the main constituent of amyloid plaques in various neurological disorders, most prominently Alzheimers disease. ... Insulin is not chemically related to inulin; the similarities in name do not relate to any similarity in form or function. ...


There are three large classes of peptides, according to how they are produced:

Ribosomal peptides 
Are synthesized by translation of mRNA. They are often subjected to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules. Some lower organisms produce peptides as antibiotics, such as microcin J25. Since they are translated, the amino acid residues involved are restricted to the 20 amino acids (plus selenomethionine and pyrrolysine), and posttranslational modifications thereof, such as phosphorylation, hydroxylation, sulfonation, disulfide formation, etc. In general, they are linear, although lariat structures are common.
Nonribosomal peptides 
Are synthesized using a modular enzyme complex (which functions much like a conveyor belt on a factory). Nonribosomal peptides and are confined primarily to unicellular organisms, plants, and fungi. There is a common core structure to all of these complexes, and they can contain many different modules to perform chemical manipulations on the evolving product. In general, these peptides are cyclic (often with highly-complex cyclic structures), although linear nonribosomal peptides are common. Since the system is modular and closely related to the machinery for building fatty acids and polyketides, hybrid compounds are often found. Oxazoles, thiazoles, and their reduced counterparts often indicate that the compound was synthesized in this fashion.
Digested peptides 
Are the result of nonspecific proteolysis as part of the digestive cycle. It has also been documented that, when certain food proteins such as gluten, casein, egg protein and spinach protein are broken down, opioid peptides are formed. These peptides mimic the effects of morphine, and those individuals that are unable to break them down will experience mental illness. These peptides are quite short and are given names such as casomorphine, gluten exorphine and dermorphine. Ultimately digested peptides are ribosomal peptides, although they aren't made on the ribosome of the organism that contains them.

Contents

Look up translate in Wiktionary, the free dictionary. ... The interaction of mRNA in a eukaryote cell. ... Proteolysis is the directed degradation (digestion) of proteins by cellular enzymes called proteases or by intramolecular digestion. ... A hormone (from Greek horman - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... An antibiotic is a drug that kills or slows the growth of bacteria. ... In chemistry, an amino acid is any molecule that contains both amino and carboxylic acid functional groups. ... Selenomethionine: chemical structure Selenomethionine is an amino acid containing selenium. ... Pyrrolysine is a naturally-occurring genetically-coded amino acid. ... Posttranslational modification means the chemical modification of a protein after its translation. ... Phosphorylation is the addition of a phosphate (PO4) group to a protein or a small molecule. ... Hydroxylation is any chemical process that introduces one or more hydroxyl groups (-OH) into a compound (or radical) thereby oxidising it. ... Chemical structure of sulfonic acid. ... A disulfide bond (SS-bond), also called a disulfide bridge, is a strong covalent bond between two sulfhydryl groups. ... A lasso is a loop of rope that is designed to be thrown around a target and tighten when pulled. ... Nonribosomal peptides (NRP) are a class of secondary metabolites, usually produced by microorganisms like bacteria and fungi. ... A module is a self-contained component of a system, which has a well-defined interface to the other components; something is modular if it includes or uses modules which can be interchanged as units without disassembly of the module. ... A microorganism or microbe is an organism that is so small that it is microscopic (invisible to the naked eye). ... Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... A cycle is anything round, in the physical sense (e. ... In chemistry, especially biochemistry, a fatty acid is a carboxylic acid (or organic acid), often with a long aliphatic tail (long chains), either saturated or unsaturated. ... Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. ... Oxazole is the parent compound for vast class of heteroaromatic compounds. ... Thiazole Thiazole, or 1,3-thiazole, is an organic chemical compound with the empirical formula C3H3NS. Its structure is a 5-membered ring, in which two of the corners of the ring are nitrogen and sulfur, and the other three are carbons. ... Wheat - a prime source of gluten Gluten is an amorphous ergastic protein found combined with starch in the endosperm of some cereals, notably wheat, rye, and barley. ... Casein is the predominant phosphoprotein found in fresh milk. ... A carton of free-range chicken eggs Ostrich egg Bird eggs are a common food source. ... Binomial name Spinacia oleracea L. Spinach (Spinacia oleracea) is a flowering plant in the family Amaranthaceae, native to central and southwestern Asia. ... Opioid Peptides are short sequences of amino acids which mimick the effect of opiates in the brain. ... Morphine (INN), the principal active agent in opium, is a powerful opioid analgesic drug. ... Casomorphin is a peptide sequence that is found in whey protein called casein, and which can be addictive to humans and cause an opiate effect. ... This article does not cite its references or sources. ... Dermorphine is a peptide which sometimes is found in human blood and urine. ...


Peptides in Molecular Biology

Peptides have received prominence in molecular biology in recent times. There are several reasons for this. The first and most important is that peptides allow the creation of antibodies in animals without the need to purify your protein of interest. You can simply make antigenic peptides of sections of your protein. These will suffice in making antibodies in a rabbit or mouse against your protein.


Another reason is that peptides have become instrumental in mass spectrometry, allowing the identification of proteins of interest based on peptide masses and sequence. Basic schematic of mass spectrometry Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio of ions. ...


The Grand Peptide Families

These peptides are ribosomal peptides, usually with hormonal activity. All of these peptides are synthesized by cells as longer "propeptides" or "proproteins" and truncated prior to exiting the cell. They are released into the bloodstream where they perform their signalling functions.


Vasopressin and oxytocin

Arginine vasopressin (AVP), also known as argipressin or antidiuretic hormone (ADH), is a human hormone that is mainly released when the body is low on water; it causes the kidneys to conserve water by concentrating the urine and reducing urine volume. ... Oxytocin is a hormone, found in mammals, which in humans is released mainly after stimulation of the nipples or distention of the vagina and which facilitates birth and breastfeeding. ...

The Tachykinin peptides

  • Substance P
  • Kassinin
  • Neurokinin A
  • Eledoisin
  • Neurokinin B

Tachykinins are one of the largest family of neuropeptides, found from amphibians to mammals. ... In neuroscience, Substance P is a neuropeptide: a short-chain polypeptide that functions as a neurotransmitter and as a neuromodulator. ...

Vasoactive intestinal peptides

  • VIP Vasoactive intestinal peptide
  • PACAP Pituitary adenylate cyclase activating peptide
  • PHI 27
  • PHM 27
  • GHRH 1-24 Growth hormone releasing hormone 1-24
  • Glucagon
  • Secretin

VIP is a peptide hormone containing 28 amino acid residues. ... Glucagon ball and stick model Glucagon is a 29-amino acid polypeptide acting as an important hormone in carbohydrate metabolism. ... Secretin is a peptide hormone produced in the S cells of the duodenum. ...

Pancreatic polypeptide-related peptides

  • NPY
  • PYY Peptide YY
  • APP Avian pancreatic polypeptide
  • HPP Human pancreatic polypeptide

Neuropeptide Y (NPY) is a 36 amino acid peptide neurotransmitter found in the brain and autonomic nervous system. ...

Opioid peptides

Opioid Peptides are short sequences of amino acids which mimick the effect of opiates in the brain. ... Pro-opiomelanocortin (POMC) is a precursor polypeptide that is built of 241 amino acid residues. ... Pro-opiomelanocortin (POMC) is a precursor polypeptide that is built of 241 amino acid residues. ...

Calcitonin peptides

Calcitonin is a a 32 amino acid polypeptide hormone that is produced in humans primarily by the C cells of the thyroid, and in many other animals in the ultimobranchial body. ... Amylin or Islet Amyloid Polypeptide (IAPP) is a 37-residue peptide hormone secreted by pancreatic β-cells at the same time as insulin (in a roughly 100:1 ratio). ...

Notes on terminology

  • A polypeptide is a single linear chain of amino acids.
  • A protein is one or more polypeptides more than about 50 amino acids long.
  • An oligopeptide or (simply) a peptide is a polypeptide less than 30-50 amino acids long.
  • A tripeptide has three amino acids.
  • A dipeptide has two amino acids.
  • A neuropeptide is a peptide that is active in association with neural tissue
  • A peptide hormone is a peptide that acts as a hormone.

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. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... A tripeptide is a peptide consisting of three amino acids, e. ... A dipeptide is a molecule consisting of two amino acids joined by a single peptide bond. ... A Neuropeptide is any of the variety of peptides found in neural tissue; e. ... Peptide hormones are a class of peptides that are secreted into the blood stream and have endocrine functions in living animals. ... A hormone (from Greek horman - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ...

External Links

  • Peptides Peptide protocols and bioinformatics, peptide synthesis services, and information on peptides.
  • The Journal: Peptide

See also


  Results from FactBites:
 
Peptide - Wikipedia, the free encyclopedia (733 words)
One convention is that those peptide chains that are short enough to be made synthetically from the constituent amino acids are called peptides rather than proteins.
Nonribosomal peptides and are confined primarily to unicellular organisms, plants, and fungi.
A peptide hormone is a peptide that acts as a hormone.
Peptide - definition of Peptide in Encyclopedia (303 words)
Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids.
Peptides (like proteins) occur in nature and are responsible for a wide array of functions, many of which are not yet understood.
Peptides differ from proteins, which are also long chains of amino acids, by virtue of their size.
  More results at FactBites »

 
 

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