Crystal Structure of GH 101 Endo-α-N-acetylgalactosaminidase from Bifidobacterium longum
Crystal Structure of GH 101 Endo-α-N-acetylgalactosaminidase from Bifidobacterium longum
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来自长双歧杆菌的 GH 101 Endo-α-N-乙酰氨基半乳糖苷酶的晶体结构
DOI：
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Kenji Yamamoto
中科院分区：
文献类型：
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作者：
R. Suzuki;T. Katayama;S. Fushinobu;M. Kitaoka;H. Kumagai;T. Wakagi;H. Shoun;H. Ashida;Kenji Yamamoto
内切-α-N-乙酰氨基半乳糖苷酶（endo-α）是糖苷水解酶（glycosidase，GH）家族101的一员，催化粘蛋白型O-聚糖的O-糖苷α键的水解。Endo-α具有转糖基化活性，可用于各种糖缀合物的合成。因此，阐明该酶的结构与功能关系具有重要意义。从长双歧杆菌JCM 1217中克隆了编码endo-α的基因，并对其基因产物（EngBF）进行了详细的表征。EngBF从糖缀合物释放半乳糖-N-二糖（Galβ1-3GalNAc，GNB），而不破坏聚糖或核心蛋白。本研究提供了EngBF的晶体结构，分辨率为2.25 A°。EngBF的催化结构域类似于GH 13 α-淀粉酶家族的TIM桶折叠。通过与α-淀粉酶家族的结构比较，确定EngBF的催化亲核体和酸碱催化剂残基分别为Asp 789和Glu 822。此外，通过自动对接和突变研究预测EngBF的底物识别的结构基础，并与产气荚膜梭菌菌株13（EngCP）的endo-α进行比较。EngBF和EngCP之间底物特异性的差异归因于形成底物结合口袋的区域中氨基酸序列的变化。我们目前的研究结果提供了深入了解的反应和底物识别机制的内切糖基化酶，释放粘蛋白型O-聚糖的糖缀合物。
Endo-α-N-acetylgalactosaminidase (endo-α), a member of glycoside hydrolase (GH) family 101, catalyzes the hydrolysis of O-glycosidic α linkages of mucin-type O-glycan. Endo-α can be used in the synthesis of various glycoconjugates because of its transglycosylation activity. Therefore, it is important to elucidate the structure-function relationship of this enzyme. The gene encoding endo-α from Bifidobacterium longum JCM1217 has been cloned, and its gene product (EngBF) has been characterized in detail. EngBF releases a galacto-N-biose (Galβ1-3GalNAc, GNB) from glycoconjugates without damaging either the glycan or the core protein. This study presents the crystal structure of EngBF at 2.25 A°resolution. The catalytic domain of EngBF resembles the TIM barrel fold of GH13 α-amylase family. Based on structural comparison with αamylase family, the catalytic nucleophile and acid/base catalyst residues of EngBF are determined to be Asp 789 and Glu822, respectively. Moreover, the structural basis of substrate recognition by EngBF was predicted by automated docking and mutational studies, and was compared with endo-α from Clostridium perfringens strain 13 (EngCP). The difference in substrate specificities between EngBF and EngCP is attributed to variations in amino acid sequences in the regions forming the substrate binding pocket. Results of our present study provide insights into both the reaction and substrate recognition mechanisms of endoglycosidases that liberate mucin-type O-glycan from glycoconjugates.
影响因子：
4.8
作者：
Fujita, K;Oura, F;Yamamoto, K
通讯作者：
Yamamoto, K