A ketosynthase homolog uses malonyl units to form esters in cervimycin biosynthesis
A ketosynthase homolog uses malonyl units to form esters in cervimycin biosynthesis
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DOI：
10.1038/nchembio.746
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发表时间：
2012-02-01
影响因子：
14.8
通讯作者：
Hertweck, Christian
中科院分区：
文献类型：
--
作者：
Bretschneider, Tom;Zocher, Georg;Hertweck, Christian
酮基化酶通过催化活化的酰基和丙二酰基结构单元的克莱森缩合产生大量生物活性聚酮化合物的碳骨架。在这里，我们报告说，酮合酶同源链霉菌tendae，CerJ，意外地形成丙二酸酯的生物合成过程中的cervimycin，糖苷抗生素对耐甲氧西林金黄色葡萄球菌（MRSA）。CerJ的缺失产生了一个更有活性的缺乏丙二酰侧链的cervimycin变体，体外生物转化表明CerJ能够将丙二酰，甲基丙二酰和二甲基丙二酰单元转移到糖苷上。根据系统发育分析和晶体结构的阐明，CerJ在功能和结构上位于酮合酶催化Claisen缩合和酰基-ACP穿梭之间，并且其特征在于非典型催化三联体。定点诱变和CerJ与底物复合的结构不仅使我们能够建立反应机制的模型，而且还提供了深入了解硫解酶超家族这个重要亚类的进化。
Ketosynthases produce the carbon backbones of a vast number of biologically active polyketides by catalyzing Claisen condensations of activated acyl and malonyl building blocks. Here we report that a ketosynthase homolog from Streptomyces tendae, CerJ, unexpectedly forms malonyl esters during the biosynthesis of cervimycin, a glycoside antibiotic against methicillinresistant Staphylococcus aureus (MRSA). Deletion of cerJ yielded a substantially more active cervimycin variant lacking the malonyl side chain, and in vitro biotransformations revealed that CerJ is capable of transferring malonyl, methylmalonyl and dimethylmalonyl units onto the glycoside. According to phylogenetic analyses and elucidation of the crystal structure, CerJ is functionally and structurally positioned between the ketosynthase catalyzing Claisen condensations and acyl-ACP shuttles, and it features a noncanonical catalytic triad. Site-directed mutagenesis and structures of CerJ in complex with substrates not only allowed us to establish a model for the reaction mechanism but also provided insights into the evolution of this important subclass of the thiolase superfamily.