title: Dual carbamoylations on the polyketide and glycosyl moiety by asm21 result in extended ansamitocin biosynthesis.
abstract: Carbamoylation is one of the post-PKS modifications in ansamitocin biosynthesis. A novel ansamitocinoside with carbamoyl substitution at the C-4 hydroxyl group of the N-β-D-glucosyl moiety was identified from the ansamitocin producer, Actinosynnema pretiosum. Through biotransformation, the carbamoyltransferase gene asm21 was suggested to be responsible for the carbamoylation of the glucosyl moiety. Three new derivatives without the backbone carbamoyl group were isolated from an asm21 mutant and characterized by NMR spectroscopy. Among them, 18-O-methyl-19-chloroproansamitocin was the major product and the preferred substrate for macrolactam C-7 carbamoylation by Asm21. However, Asm21 exhibited higher catalytic efficiency toward the glucosyl moiety. Furthermore, the dual carbamoylations and N-glycosylation were precisely demonstrated in vivo. This work represents the first biochemical characterization of an O-carbamoyltransferase performing dual actions on both a polyketide backbone and a glycosyl moiety during ansamitocin biosynthesis.
authors.affiliation: State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Peiji
authors.initials: P
authors.lastname: Zhao
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Kang
authors.forename: Juan
authors.initials: J
authors.lastname: Ma
authors.forename: Linquan
authors.initials: L
authors.lastname: Bai
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
mesh_terms: D000192:Actinomycetales / Q000201:enzymology; D055162:Biocatalysis; D019878:Carboxyl and Carbamoyl Transferases / Q000235:genetics / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008453:Maytansine / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry; D009154:Mutation; D061065:Polyketides / Q000737:chemistry*
chemical_list: D061065:Polyketides; D008453:Maytansine; C015682:ansamitocins; D019878:Carboxyl and Carbamoyl Transferases