Chemoenzymatic Approach to Enantiopure Streptogramin B Variants: Characterization of Stereoselective Pristinamycin I Cyclase from Streptomyces pristinaespiralis
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- 作者：Christoph Mahlert ; Stephan A. Sieber ; Jan Grü ; newald ; and Mohamed A. Marahiel
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：July 6, 2005
- 年：2005
- 卷：127
- 期：26
- 页码：9571 - 9580
- 全文大小：635K
- 年卷期：v.127,no.26(July 6, 2005)
- ISSN：1520-5126
文摘
Streptogramin B antibiotics are cyclic peptide natural products produced by Streptomyces species.In combination with the synergistic group A component, they are "last line of defense" antimicrobial agentsagainst multiresistant cocci. The racemization sensitivity of the phenylglycine (Phg7) ester is a complexchallenge in total chemical synthesis of streptogramin B molecules. To provide fast and easy access tonovel streptogramin antibiotics, we introduce a novel chemoenzymatic strategy in which diversity is generatedby standard solid phase protocols and stereoselectivity by subsequent enzymatic cyclization. For thisapproach, we cloned, overproduced, and biochemically characterized the recombinant thioesterase domainSnbDE TE of the pristinamycin I nonribosomal peptide synthetase from Streptomyces pristinaespiralis.SnbDE TE catalyzes regioselective ring closure of linear peptide thioester analogues of pristinamycin I aswell as stereoselective cyclization out of complex in situ racemizing substrate mixtures, enabling synthesisof Streptogramin B variants via a dynamic kinetic resolution assay. A remarkable substrate tolerance wasdetected for the enzymatic cyclization including all the seven positions of the peptide backbone. Interestingly,SnbDE TE was observed to be the first cyclase from a macrolactone forming NRPS which is additionallyable to catalyze macrolactamization of peptide thioester substrates. An N-methylated peptide bond betweenpositions 4 and 5 is mandatory for a high substrate turnover. The presented strategy is potent to screen foranalogues with improved activity and guides our understanding of structure-activity relationships in theimportant class of streptogramin antibiotics.