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Encyclopedia > Polyketide

Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. Secondary metabolites seem to be unnecessary for an organism’s ontogeny, but appear to have applications such as defence and intercellular communication. Polyketides are derived from the polymerization of acetyl and propionyl subunits in a similar process to fatty acid synthesis. They also serve as building blocks for a broad range of natural products or are derivatized. Secondary metabolites, also known as natural products, are those products (chemical compounds) of metabolism that are not essential for normal growth, development or reproduction of an organism. ... 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. ... Divisions Chytridiomycota Zygomycota Ascomycota Basidiomycota The Fungi (singular: fungus) are a large group of organisms ranked as a kingdom within the Domain Eukaryota. ... For other uses, see Plant (disambiguation). ... Animalia redirects here. ... Ontogeny (also ontogenesis or morphogenesis) describes the origin and the development of an organism from the fertilized egg to its mature form. ... Acetyl is the radical of acetic acid. ... Fatty acids are an important source of energy for many organisms. ... Secondary metabolites, also known as natural products, are those products (chemical compounds) of metabolism that are not essential for normal growth, development or reproduction of an organism. ... Derivatization is a technique used in Chemistry which transforms a chemical Compound into a Product of similar chemical Structure, called Derivate. ...


Polyketides are structurally a very diverse family of natural products with an extremely broad range of biological activities and pharmacological properties. Polyketide antibiotics, antifungals, cytostatics, anticholesterolemics, antiparasitics, coccidiostatics, animal growth promotants and natural insecticides are in commercial use. Staphylococcus aureus - Antibiotics test plate. ... Something antifungal kills or inhibits the growth of fungus. ... Chemotherapy is the use of chemical substances to treat disease. ... An insecticide is a pesticide used against insects in all developmental forms. ...


Examples

The macrolides are a group of drugs (typically antibiotics) whose activity stems from the presence of a macrolide ring, a large lactone ring to which one or more deoxy sugars, usually cladinose and desosamine, are attached. ... Staphylococcus aureus - Antibiotics test plate. ... Erythromycin is a macrolide antibiotic which has an antimicrobial spectrum similar to or slightly wider than that of penicillin, and is often used for people who have an allergy to penicillins. ... Clarithromycin is a macrolide antibiotic used to treat pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, pneumonia (especially atypical pneumonias associated with Chlamydia pneumoniae or TWAR), skin and skin structure infections, and, in HIV and AIDS patients to prevent, and to treat, disseminated Mycobacterium avium complex or... Azithromycin is an azalide, a subclass of macrolide antibiotics. ... Immunosuppression is the medical suppression of the immune system. ... Tacrolimus (also FK-506 or Fujimycin) is a 23-membered macrolide lactone discovered in 1984 from the fermentation broth of a Japanese soil sample that contained the bacteria Streptomyces tsukubaensis. ... Polyenes are poly-unsaturated organic compounds that contain one or more sequences of alternating double and single carbon-carbon bonds. ... Staphylococcus aureus - Antibiotics test plate. ... Amphotericin B (Fungilin®, Fungizone®, Abelcet®, AmBisome®, Amphocil®) is a polyene antimycotic drug, used intravenously in systemic fungal infections. ... Tetracycline (INN) (IPA: ) is a broad-spectrum antibiotic produced by the streptomyces bacterium, indicated for use against many bacterial infections. ... Staphylococcus aureus - Antibiotics test plate. ... (+)-Discodermolide is a novel polyketide natural product found to be a potent inhibitor of tumor cell growth. ...

Biosynthesis

The biosynthesis of polyketides shares striking similarities with the fatty acid biosynthesis. Polyketides are synthesized by one or more specialized polyketide-synthase (PKS) enzymes. The PKS genes for a certain polyketide are usually organized in one operon in bacteria and in gene clusters in eukaryotes. The type I polyketide-synthases are large, highly modular proteins, while type II polyketide-synthases are aggregates of monofunctional proteins. Biosynthesis is a phenomenon where chemical compounds are produced from simpler reagents. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... An operon is a group of key nucleotide sequences including an operator, a common promoter, and one or more structural genes that are controlled as a unit to produce messenger RNA (mRNA). ... A gene cluster is a set of two or more genes that serve to encode for the same or similar products. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Protista A eukaryote (IPA: ) is an organism with a complex cell or cells, in which the genetic material is organized into a membrane-bound nucleus or nuclei. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...


Each type I polyketide-synthase module consists of several domains with defined functions, separated by short spacer regions. The order of modules and domains of a complete polyketide-synthase is as follows (in the order N-terminus to C-terminus): In biology, a domain (also superregnum, superkingdom, or empire) is the top-level grouping of organisms in scientific classification, higher than a kingdom. ... The N-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free amine group (NH2). ... The C-terminal end refers to the extremity of a protein or polypeptide terminated by an amino acid with a free carboxyl group (COOH). ...

  • Starting or loading module: AT-ACP-
  • Elongation or extending modules: -KS-AT-[DH-ER-KR]-ACP-
  • Termination or releasing module: -TE

Domains:

The polyketide chain and the starter groups are bound with their carboxy group to the SH groups of the ACP and the KS domain through a thioester linkage: R-C(=O)OH + HS-protein <=> R-C(=O)S-protein + H2O. The growing chain is handed over from one SH group to the next by trans-acylations and is releases at the end by hydrolysis or by cyclization (alcoholysis or aminolysis). The acyl carrier protein is an important component in both fatty acid biosynthesis and polyketide synthases, with the growing polyketide chain bound during synthesis as a thiol ester at the distal thiol of a 4-phophopantethiene moiety. ... // In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... A cofactor is the following: In mathematics a cofactor is the minor of an element of a square matrix. ... Serine is one of the 20 natural amino acids. ... 4-Phosphopantetheine is an essential prosthetic group of acyl carrier protein (ACP) and peptidyl carrier proteins (PCP) and aryl carrier proteins (ArCP) derived from Coenzyme A. Phosphopantetheine fulfils two demands. ... // In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... Cysteine is a naturally occurring amino acid which has a thiol group and is found in most proteins, though only in small quantities. ... 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 thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... Thioesters are compounds resulting from the bonding of sulfur with an acyl group (an alkyl group attached to a carbon-oxygen double bond), with the general formula R-S-CO-R. Some biochemists believe that the thioester bond was critical for the origin of life. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ... General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Atomic mass 32. ... Water is a chemical substance that is essential to all known forms of life. ... // In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). ... Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula H2O. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water. ... Aminolysis is any chemical reaction in which a molecule is split into two parts by reacting with a molecule of ammonia or an amine. ...


Starting stage:

  • The starter group, usually acetyl-CoA or malonyl-CoA, is loaded onto the ACP domain of the starter module catalyzed by the starter module's AT domain.

Elongation stages: Categories: Biochemistry stubs | Thiols ... -1...

  • The polyketide chain is handed over from the ACP domain of the previous module to the KS domain of the current module, catalyzed by the KS domain.
  • The elongation group, usually malonyl-CoA or methyl-malonyl-CoA, is loaded onto the current ACP domain catalyzed by the current AT domain.
  • The ACP-bound elongation group reacts in a Claisen condensation with the KS-bound polyketide chain under CO2 evolution, leaving a free KS domain and an ACP-bound elongated polyketide chain. The reaction takes place at the KSn-bound end of the chain, so that the chain moves out one position and the elangation group becomes the new bound group.
  • Optionally, the fragment of the polyketide chain can be altered stepwise by additional domains. The KR (keto-reductase) domain reduces the β-keto group to a β-hydroxy group, the DH (dehydratase) domain splits off H2O, resulting in the α-β-unsaturated alkene, and the ER (enoyl-reductase) domain reduces the α-β-double-bond to a single-bond. It is important to note that these modification domains actually affect the previous addition to the chain (i.e. the group added in the previous module), not the component recruited to the ACP domain of the module containing the modification domain.
  • This cycle is repeated for each elongation module.

Termination stage:-1... The Claisen condensation is a carbon-carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... Water is a chemical substance that is essential to all known forms of life. ... The chemical structure of ethylene, the simplest alkene. ... Covalent bonding is a description of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. ... Covalent bonding is a description of chemical bonding that is characterized by the sharing of pairs of electrons between atoms. ...

  • The TE (thio-esterase) domain hydrolyzes the completed polyketide chain from the ACP-domain of the previous module.

Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of water, which has the chemical formula H2O. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water. ...

See also


  Results from FactBites:
 
Peter Leadlay Research Group, Polyketide Antibiotic Biosynthesis (637 words)
Polyketides are natural products which provide a staggering range of clinically effective drugs.
Subsequently, the polyketide chain is extended by condensation with methylmalonate (from methylmalonyl CoA) pre-loaded on the ACP domain of an extension module.
The polyketide is then released from the enzyme by a thioesterase domain and post PKS enzymes such as glycosyl- and methyltransferases complete the biosynthesis.
polyketide: Information from Answers.com (561 words)
Polyketides are secondary metabolites from bacteria, fungi, plants, and animals.
Polyketides are derived from the polymerization of acetyl and propionyl subunits in a similar process to fatty acid synthesis.
The PKS genes for a certain polyketide are usually organized in one operon in bacteria and in gene clusters in eukaryotes.
  More results at FactBites »

 
 

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