Research Faculty of Agriculture, Hokkaido University, Sapporo, Japan.
Faculty of Advanced Life Science, Hokkaido University, Sapporo, Japan.
FEBS Lett. 2018 Jul;592(13):2268-2281. doi: 10.1002/1873-3468.13126. Epub 2018 Jun 20.
α-Glucosidase hydrolyzes α-glucosides and transfers α-glucosyl residues to an acceptor through transglucosylation. In this study, GH13_31 α-glucosidase BspAG13_31A with high transglucosylation activity is reported in Bacillus sp. AHU2216 and biochemically and structurally characterized. This enzyme is specific to α-(1→4)-glucosidic linkage as substrates and transglucosylation products. Maltose is the most preferred substrate. Crystal structures of BspAG13_31A wild-type for the substrate-free form and inactive acid/base mutant E256Q in complexes with maltooligosaccharides were solved at 1.6-2.5 Å resolution. BspAG13_31A has a catalytic domain folded by an (β/α) -barrel. In subsite +1, Ala200 and His203 on β→α loop 4 and Asn258 on β→α loop 5 are involved in the recognition of maltooligosaccharides. Structural basis for specificity of GH13_31 enzymes to α-(1→4)-glucosidic linkage is first described.
α-葡萄糖苷酶水解α-葡萄糖苷，并通过转糖苷作用将α-葡萄糖基残基转移到受体上。在这项研究中，报道了来自芽孢杆菌 AHU2216 的具有高转糖苷活性的 GH13_31 α-葡萄糖苷酶 BspAG13_31A，并对其进行了生物化学和结构表征。该酶对底物和转糖苷产物具有特异性α-(1→4)-糖苷键。麦芽糖是最优选的底物。BspAG13_31A 野生型的无底物形式和与麦芽寡糖复合物中的无活性酸碱突变体 E256Q 的晶体结构在 1.6-2.5 Å 分辨率下得到解决。BspAG13_31A 由（β/α）-桶折叠的催化结构域。在 +1 亚位，β→α 环 4 上的 Ala200 和 His203 和β→α 环 5 上的 Asn258 参与了麦芽寡糖的识别。首次描述了 GH13_31 酶对α-(1→4)-糖苷键特异性的结构基础。
