AvmM catalyses macrocyclization through dehydration/Michael-type addition in alchivemycin A biosynthesis
Hong Jie Zhu, Bo Zhang, Wanqing Wei, Shuang He Liu, Lang Xiang, Jiapeng Zhu, Rui Jiao, Yasuhiro Igarashi, Ghader Bashiri, Yong Liang, Ren Xiang Tan, Hui Ming Ge
Abstract
Macrocyclization is an important process that affords morphed scaffold in biosynthesis of bioactive natural products. Nature has adapted diverse biosynthetic strategies to form macrocycles. In this work, we report the identification and characterization of a small enzyme AvmM that can catalyze the construction of a 16-membered macrocyclic ring in the biosynthesis of alchivemycin A (1). We show through in vivo gene deletion, in vitro biochemical assay and isotope labelling experiments that AvmM catalyzes tandem dehydration and Michael-type addition to generate the core scaffold of 1. Mechanistic studies by crystallography, DFT calculations and MD simulations of AvmM reveal that the reactions are achieved with assistance from the special tenuazonic acid like moiety of substrate. Our results thus uncover an uncharacterized macrocyclization strategy in natural product biosynthesis.