Crystal structure of the catalytic unit of GH87-type α-1,3-glucanase Agl-KA from Bacillus circulans
Crystal structure of the catalytic unit of GH87-type α-1,3-glucanase Agl-KA from Bacillus circulans
复制标题
环状芽孢杆菌GH87型α-1,3-葡聚糖酶Agl-KA催化单元的晶体结构
DOI：
10.1038/s41598-019-51822-5
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发表时间：
2019
影响因子：
4.6
通讯作者：
K. Makabe
中科院分区：
文献类型：
--
作者：
S. Yano;W. Suyotha;N. Oruro;T. Matsui;S. Shiga;T. Itoh;T. Hibi;Y. Tanaka;M. Wakayama;K. Makabe
糖苷水解酶（GH）87型α-1，3-葡聚糖酶水解α-1，3-葡聚糖中的α-1，3-糖苷键，α-1，3-葡聚糖存在于真菌细胞壁和由口腔链球菌产生的胞外多糖中。本文报道了用X射线晶体衍射法测定的环状芽孢杆菌GH 87型α-1，3-葡聚糖酶催化单元Agl-KA的分子结构。该催化单元由两个串联结构域（N-末端半乳糖结合样结构域和C-末端右手β-螺旋结构域）组成。虽然β-螺旋结构域广泛存在于多糖加工酶中，但首次观察到与半乳糖结合样结构域形成复合物。生化分析表明，Asp 1067，Asp 1090和Asp 1091是重要的催化，这些残基确实位于假定的底物结合裂缝，形成一个封闭的末端，并解释了产品的特异性。
Glycoside hydrolase (GH) 87-type α-1,3-glucanase hydrolyses the α-1,3-glucoside linkages of α-1,3-glucan, which is found in fungal cell walls and extracellular polysaccharides produced by oralStreptococci. In this study, we report on the molecular structure of the catalytic unit of GH 87-type α-1,3-glucanase, Agl-KA, fromBacillus circulans, as determined by x-ray crystallography at a resolution of 1.82 Å. The catalytic unit constitutes a complex structure of two tandemly connected domains—the N-terminal galactose-binding-like domain and the C-terminal right-handed β-helix domain. While the β-helix domain is widely found among polysaccharide-processing enzymes, complex formation with the galactose-binding-like domain was observed for the first time. Biochemical assays showed that Asp1067, Asp1090 and Asp1091 are important for catalysis, and these residues are indeed located at the putative substrate-binding cleft, which forms a closed end and explains the product specificity.