Type III polyketide synthase beta-ketoacyl-ACP starter unit and ethylmalonyl-CoA extender unit selectivity discovered by Streptomyces coelicolor genome mining |
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Authors: | Song Lijiang Barona-Gomez Francisco Corre Christophe Xiang Longkuan Udwary Daniel W Austin Michael B Noel Joseph P Moore Bradley S Challis Gregory L |
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Institution: | Department of Chemistry, University of Warwick, Coventry CV4 7AL, U.K |
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Abstract: | Polyketide synthases (PKSs) are involved in the biosynthesis of many important natural products. In bacteria, type III PKSs typically catalyze iterative decarboxylation and condensation reactions of malonyl-CoA building blocks in the biosynthesis of polyhydroxyaromatic products. Here it is shown that Gcs, a type III PKS encoded by the sco7221 ORF of the bacterium Streptomyces coelicolor, is required for biosynthesis of the germicidin family of 3,6-dialkyl-4-hydroxypyran-2-one natural products. Evidence consistent with Gcs-catalyzed elongation of specific beta-ketoacyl-ACP products of the fatty acid synthase FabH with ethyl- or methylmalonyl-CoA in the biosynthesis of germicidins is presented. Selectivity for beta-ketoacyl-ACP starter units and ethylmalonyl-CoA as an extender unit is unprecedented for type III PKSs, suggesting these enzymes may be capable of utilizing a far wider range of starter and extender units for natural product assembly than believed until now. |
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