期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 287, 期 52, 页码 43288-43299出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M112.416511
关键词
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资金
- Mizutani Foundation for Glycoscience
- Swedish Research Council Formas (via the European Union WoodWisdom-Net ERA-NET)
- Swedish Research Council Formas (via Carbo-Mat-the KTH Advanced Carbohydrate Materials Centre)
- Biotechnology and Biological Sciences Research Council [BB/I014802/1]
- BBSRC [BB/I014802/1] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/I014802/1] Funding Source: researchfish
The metabolism of the storage polysaccharides glycogen and starch is of vital importance to organisms from all domains of life. In bacteria, utilization of these alpha-glucans requires the concerted action of a variety of enzymes, including glycoside hydrolases, glycoside phosphorylases, and transglycosylases. In particular, transglycosylases from glycoside hydrolase family 13 (GH13) and GH77 play well established roles in alpha-glucan side chain (de) branching, regulation of oligo-and polysaccharide chain length, and formation of cyclic dextrans. Here, we present the biochemical and tertiary structural characterization of a new type of bacterial 1,4-alpha-glucan 4-alpha-glucosyltransferase from GH31. Distinct from 1,4-alpha-glucan 6-alpha-glucosyltransferases (EC 2.4.1.24) and 4-alpha-glucanotransferases (EC 2.4.1.25), this enzyme strictly transferred one glucosyl residue from alpha(1 -> 4)-glucans in disproportionation reactions. Substrate hydrolysis was undetectable for a series of malto-oligosaccharides except maltose for which transglycosylation nonetheless dominated across a range of substrate concentrations. Crystallographic analysis of the enzyme in free, acarbose-complexed, and trapped 5-fluoro-beta-glucosyl-enzyme intermediate forms revealed extended substrate interactions across one negative and up to three positive subsites, thus providing structural rationalization for the unique, single monosaccharide transferase activity of the enzyme.
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