Polyketide
Oxford Dictionary of Biochemistry:
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polyketide
or (sometimes) acetogenin
any natural product synthesized via linear poly-β-ketones, which are themselves formed by repetitive head-to-tail addition of acetyl (or substituted acetyl) units indirectly derived from acetate (or a substituted acetate) by a mechanism similar to that for fatty-acid biosynthesis but without the intermediate reductive steps. In many cases, acetyl-CoA functions as the starter unit and malonyl-CoA as the extending unit. Various molecules other than acetyl-CoA may be used as starter, often with methylmalonyl-CoA as the extending unit. The poly-β-ketones so formed may undergo modification by alkylation, cyclization, glycosylation, oxidation, or reduction. Polyketides include: coniine (of hemlock) and orsellinate (of lichens) — acetyl-CoA; flavanoids and stilbenes — cinnamoyl-CoA; tetracyclines — amide of malonyl-CoA; urushiols (of poison-ivy) — palmitoleoyl-CoA; erythronolides — propionyl-CoA and methylmalonyl-CoA as extender. Polyketide synthases are large multidomain proteins that contain phosphopantheteine.
any natural product synthesized via linear poly-β-ketones, which are themselves formed by repetitive head-to-tail addition of acetyl (or substituted acetyl) units indirectly derived from acetate (or a substituted acetate) by a mechanism similar to that for fatty-acid biosynthesis but without the intermediate reductive steps. In many cases, acetyl-CoA functions as the starter unit and malonyl-CoA as the extending unit. Various molecules other than acetyl-CoA may be used as starter, often with methylmalonyl-CoA as the extending unit. The poly-β-ketones so formed may undergo modification by alkylation, cyclization, glycosylation, oxidation, or reduction. Polyketides include: coniine (of hemlock) and orsellinate (of lichens) — acetyl-CoA; flavanoids and stilbenes — cinnamoyl-CoA; tetracyclines — amide of malonyl-CoA; urushiols (of poison-ivy) — palmitoleoyl-CoA; erythronolides — propionyl-CoA and methylmalonyl-CoA as extender. Polyketide synthases are large multidomain proteins that contain phosphopantheteine.
| polykaryocyte, polyion, polyhydric | |
| polylabelling, polylinker, polymannan |
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Polyketide
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Polyketide
Polyketides are secondary metabolites from bacteria, fungi, plants, and animals. Polyketides are usually biosynthesized through the decarboxylative condensation of malonyl-CoA derived extender units in a similar process to fatty acid synthesis (a Claisen condensation). [1] The polyketide chains produced by a minimal polyketide synthase are often further derivitized and modified into bioactive natural products.
Polyketides are structurally a very diverse family of natural products with diverse biological activities and pharmacological properties. They are broadly divided into three classes: type I polyketides (often macrolides produced by multimodular megasynthases), type II polyketides (often aromatic molecules produced by the iterative action of dissociated enzymes), and type III polyketides (often small aromatic molecules produced by fungal species). Polyketide antibiotics, antifungals, cytostatics, anticholesteremic, antiparasitics, coccidiostats, animal growth promoters and natural insecticides are in commercial use.[citation needed]
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Contents
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Examples
- Macrolides
- Pikromycin, the first isolated macrolide (1951[2])
- The antibiotics erythromycin A, clarithromycin, and azithromycin
- The immunosuppressant tacrolimus (FK506)
- Radicicol and Pochonin family (HSP90 inhibitor)
- Polyene antibiotics
- Tetracyclines
- The tetracycline family of antibiotics
- Acetogenins
- Bullatacin
- Squamocin
- Molvizarin
- Uvaricin
- Annonacin
- Others
Biosynthesis
Polyketides are synthesized by one or more specialized and highly complex polyketide synthase (PKS) enzymes. [1]
See also
References
- ^ a b Robinson JA (1991). "Polyketide synthase complexes: their structure and function in antibiotic biosynthesis". Philos Trans R Soc Lond B Biol Sci. 332 (1263): 107–114. doi:10.1098/rstb.1991.0038. PMID 1678529.
- ^ Brockmann, H. and Henkel, W. (1951). "Pikromycin, ein bitter schmeckendes Antibioticum aus Actinomyceten". ntibiotica aus Actinomyceten, 84: 184–288. doi:10.1002/cber.19510840306.
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Oxford Dictionary of Biochemistry
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