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首页> 外文期刊>Journal of Molecular Biology >Crystal structures and mutagenesis of sucrose hydrolase from Xanthomonas axonopodis pv. glycines: insight into the exclusively hydrolytic amylosucrase fold.
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Crystal structures and mutagenesis of sucrose hydrolase from Xanthomonas axonopodis pv. glycines: insight into the exclusively hydrolytic amylosucrase fold.

机译：轴突黄单胞菌蔗糖水解酶的晶体结构和诱变作用。甘氨酸：深入了解水解淀粉酶的折叠。

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摘要

Neisseria polysaccharea amylosucrase (NpAS), a transglucosidase of glycoside hydrolase family 13, is a hydrolase and glucosyltransferase that catalyzes the synthesis of amylose-like polymer from a sucrose substrate. Recently, an NpAS homolog from Xanthomonas axonopodis pv. glycines was identified as a member of the newly defined carbohydrate utilization locus that regulates the utilization of plant sucrose in phytopathogenic bacteria. Interestingly, this enzyme is exclusively a hydrolase and not a glucosyltransferase; it is thus known as sucrose hydrolase (SUH). Here, we elucidated the novel functional features of SUH using X-ray crystallography and site-directed mutagenesis. Four different crystal structures of SUH, including the SUH-Tris and the SUH-sucrose and SUH-glucose complexes, represent structural snapshots along the catalytic reaction coordinate. These structures show that SUH is distinctly different from NpAS in that ligand-induced conformational changes in SUH cause the formation of a pocket-shaped active site and in that SUH lacks the three arginine residues found in the NpAS active site that appear to be crucial for NpAS glucosyltransferase activity. Mutation of SUH to insert these arginines failed to confer glucosyltransferase activity, providing evidence that its enzymatic activity is limited to sucrose hydrolysis by its pocket-shaped active site and the identity of residues in the vicinity of the active site.
机译：Nesseria polysaccharea淀粉酶（NpAS）是糖苷水解酶家族13的转葡糖苷酶，是一种水解酶和葡萄糖基转移酶，可催化从蔗糖底物中合成直链淀粉样聚合物。最近，来自Xanthomonas axonopodis pv的NpAS同源物。甘氨酸被确定为新定义的碳水化合物利用位点的成员，该位点可调节植物致病菌中植物蔗糖的利用。有趣的是，该酶仅是水解酶，而不是葡萄糖基转移酶。因此，它被称为蔗糖水解酶（SUH）。在这里，我们通过X射线晶体学和定点诱变阐明了SUH的新功能特征。 SUH的四个不同晶体结构，包括SUH-Tris和SUH-蔗糖以及SUH-葡萄糖复合物，代表了沿催化反应坐标的结构快照。这些结构表明，SUH与NpAS明显不同，在于SUH中配体诱导的构象变化导致形成口袋状的活性位点，并且SUH缺少在NpAS活性位点中发现的三个精氨酸残基，这些残基似乎对NpAS至关重要。 NpAS葡萄糖基转移酶活性。插入这些精氨酸的SUH突变未能赋予葡糖基转移酶活性，提供了证据表明其酶活性仅限于蔗糖水解，其囊状活性位点和活性位点附近的残基相同。

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