Biochemical and Structural Insights into the Aminotransferase CrmG in Caerulomycin Biosynthesis
Biochemical and Structural Insights into the Aminotransferase CrmG in Caerulomycin Biosynthesis
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青霉素生物合成中转氨酶 CrmG 的生化和结构见解
DOI：
10.1021/acschembio.5b00984
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发表时间：
2016
影响因子：
4
通讯作者：
Zhang Changsheng
中科院分区：
文献类型：
--
作者：
Zhu Yiguang;Xu Jinxin;Mei Xiangui;Feng Zhan;Zhang Liping;Zhang Qingbo;Zhang Guangtao;Zhu Weiming;Liu Jinsong;Zhang Changsheng
天蓝霉素A（Caerulomycin A，CRM A1）是一类具有2，2 ′-联吡啶环结构的天然产物，是一种新型的免疫抑制剂。在此，我们报告的功能特性，动力学分析，底物特异性，和结构的见解转氨酶CrmG in 1生物合成。氨基转移酶CrmG被证实催化1生物合成途径中的关键转氨反应，将醛基转化为氨基，优选l-谷氨酸和l-谷氨酰胺作为氨基供体底物。与辅因子5′-磷酸吡哆醛（PLP）或5′-磷酸吡哆胺（PMP）或受体底物复合的CrmG的晶体结构被确定为采用具有独特的小附加结构域的PLP依赖性酶的典型折叠I型。结构导向的定点突变确定了底物结合和催化活性的关键氨基酸残基，从而为CrmG的转氨机制提供了见解。
Caerulomycin A (CRM A1) belongs to a family of natural products containing a 2,2′-bipyridyl ring core structure and is currently under development as a potent novel immunosuppressive agent. Herein, we report the functional characterization, kinetic analysis, substrate specificity, and structure insights of an aminotransferase CrmG in1biosynthesis. The aminotransferase CrmG was confirmed to catalyze a key transamination reaction to convert an aldehyde group to an amino group in the1biosynthetic pathway, preferringl-glutamate andl-glutamine as the amino donor substrates. The crystal structures of CrmG in complex with the cofactor 5′-pyridoxal phosphate (PLP) or 5′-pyridoxamine phosphate (PMP) or the acceptor substrate were determined to adopt a canonical fold-type I of PLP-dependent enzymes with a unique small additional domain. The structure guided site-directed mutagenesis identified key amino acid residues for substrate binding and catalytic activities, thus providing insights into the transamination mechanism of CrmG.