title: Characterizing amosamine biosynthesis in amicetin reveals AmiG as a reversible retaining glycosyltransferase.
abstract: The antibacterial and antiviral agent amicetin is a disaccharide nucleoside antibiotic featuring a unique α-(1→4)-glycoside bond between amosamine and amicetose, characteristic of a retaining glycosylation. In this study, two key steps for amosamine biosynthesis were investigated: the N-methyltransferase AmiH was demonstrated to be requisite for the dimethylation in amosamine, and the glycosyltransferase AmiG was shown to be necessary for amosaminylation. Biochemical and kinetic characterization of AmiG revealed for the first time the catalytic reversibility of a retaining glycosyltransferase involved in secondary metabolite biosynthesis. AmiG displayed substrate flexibility by utilizing five additional sugar nucleotides as surrogate donors. AmiG was also amenable to sugar and aglycon exchange reactions. This study indicates that AmiG is a potential catalyst for diversifying nucleoside antibiotics and paves the way for mechanistic studies of a natural-product retaining glycosyltransferase.
authors.affiliation: CAS Key Laboratory of Tropical Marine Bio-resources and Ecology, RNAM Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, 164 West Xingang Road, Guangzhou 510301, China.
authors.forename: Ruidong
authors.initials: R
authors.lastname: Chen
authors.forename: Haibo
authors.initials: H
authors.lastname: Zhang
authors.forename: Gaiyun
authors.initials: G
authors.lastname: Zhang
authors.forename: Sumei
authors.initials: S
authors.lastname: Li
authors.forename: Guangtao
authors.initials: G
authors.lastname: Zhang
authors.forename: Yiguang
authors.initials: Y
authors.lastname: Zhu
authors.forename: Jinsong
authors.initials: J
authors.lastname: Liu
authors.forename: Changsheng
authors.initials: C
authors.lastname: Zhang
mesh_terms: D000588:Amines / Q000378:metabolism*; D000606:Amino Sugars / Q000737:chemistry* / Q000378:metabolism*; D016695:Glycosyltransferases / Q000378:metabolism*; D007700:Kinetics; D011741:Pyrimidine Nucleosides / Q000378:metabolism; D013302:Streptomyces / Q000201:enzymology
chemical_list: D000588:Amines; D000606:Amino Sugars; D011741:Pyrimidine Nucleosides; C004413:amicetin; D016695:Glycosyltransferases