Biochemical and Structural Insights into the Aminotransferase CrmG in Caerulomycin Biosynthesis

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• 作者：Yiguang Zhu ; Jinxin Xu ; Xiangui Mei ; Zhan Feng ; Liping Zhang ; Qingbo Zhang ; Guangtao Zhang ; Weiming Zhu ; Jinsong Liu ; Changsheng Zhang
• 刊名：ACS Chemical Biology
• 出版年：2016
• 出版时间：April 15, 2016
• 年：2016
• 卷：11
• 期：4
• 页码：943-952
• 全文大小：638K
• 年卷期：0
• ISSN：1554-8937

文摘

Caerulomycin A (CRM A 1) 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 in 1 biosynthesis. The aminotransferase CrmG was confirmed to catalyze a key transamination reaction to convert an aldehyde group to an amino group in the 1 biosynthetic pathway, preferring l-glutamate and l-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.