Crystal structure of Cel44A, a glycoside hydrolase family 44 endoglucanase from Clostridium thermocellum
Crystal structure of Cel44A, a glycoside hydrolase family 44 endoglucanase from Clostridium thermocellum
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DOI：
10.1074/jbc.m706835200
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发表时间：
2007-12-07
影响因子：
4.8
通讯作者：
Tanaka, Isao
中科院分区：
文献类型：
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作者：
Kitago, Yu;Karita, Shuichi;Tanaka, Isao
Cel44A 是热纤梭菌纤维素体的酶成分之一，其晶体结构以 0.96 埃的分辨率解析。该酶属于糖苷水解酶家族（GH家族）44。结构表明Cel44A由TIM样桶状结构域和β-夹心结构域组成。与底物复合的野生型和E186Q突变体结构表明两个谷氨酸残基Glu(186)和Glu(359)是该酶的活性残基。进行生化实验来证实这个想法。结构特征表明GH家族44属于GH-A家族，Cel44A催化的反应为保留型水解。使用还原纤维寡糖作为底物，通过 H-1 NMR 实验证实了水解的立体化学过程。
The crystal structure of Cel44A, which is one of the enzymatic components of the cellulosome of Clostridium thermocellum, was solved at a resolution of 0.96 angstrom. This enzyme belongs to glycoside hydrolase family (GH family) 44. The structure reveals that Cel44A consists of a TIM-like barrel domain and a beta-sandwich domain. The wild-type and the E186Q mutant structures complexed with substrates suggest that two glutamic acid residues, Glu(186) and Glu(359), are the active residues of the enzyme. Biochemical experiments were performed to confirm this idea. The structural features indicate that GH family 44 belongs to clan GH-A and that the reaction catalyzed by Cel44A is retaining type hydrolysis. The stereochemical course of hydrolysis was confirmed by a H-1 NMR experiment using the reduced cellooligosaccharide as a substrate.