The structural basis for catalysis and specificity of the Pseudomonas cellulosa α-glucuronidase, GlcA67A
The structural basis for catalysis and specificity of the Pseudomonas cellulosa α-glucuronidase, GlcA67A
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DOI：
10.1016/s0969-2126(02)00742-6
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发表时间：
2002-04-01
期刊：
影响因子：
5.7
通讯作者：
Davies, GJ
中科院分区：
文献类型：
--
作者：
Nurizzo, D;Nagy, T;Davies, GJ
α-葡糖醛酸糖苷酶是光合生物质再循环的核心酶系的组分，从木聚糖中除去α-1，2连接的4-O-甲基葡糖醛酸。来自纤维假单胞菌的α-葡糖醛酸糖苷酶GlcA 67 A的结构揭示了三个结构域，其中心是容纳催化装置的（β/α）（B）桶。复合物的酶与个别反应产物，无论是木二糖或葡萄糖醛酸，和三元复合物的葡萄糖醛酸和木三糖揭示了一个“盲”口袋选择短装饰木寡糖取代糖醛酸在其非还原性结束，与动力学数据一致。催化中心揭示了一个星座的羧酸盐; Glu 292是准备提供质子援助离开基团离开与Glu 393和Asp 365都适当定位，以提供碱催化的援助，用于反转亲核攻击水。
alpha-glucuronidases, components of an ensemble of enzymes central to the recycling of photosynthetic biomass, remove the alpha-1,2 linked 4-O-methyl glucuronic acid from xylans. The structure of the alpha-glucuronidase, GlcA67A, from Pseudomonas cellulosa reveals three domains, the central of which is a (beta/alpha)(B) barrel housing the catalytic apparatus. Complexes of the enzyme with the individual reaction products, either xylobiose or glucuronic acid, and the ternary complex of both glucuronic acid and xylotriose reveal a "blind" pocket which selects for short decorated xylooligosaccharides substituted with the uronic acid at their nonreducing end, consistent with kinetic data. The catalytic center reveals a constellation of carboxylates; Glu292 is poised to provide protonic assistance to leaving group departure with Glu393 and Asp365 both appropriately positioned to provide base-catalyzed assistance for inverting nucleophilic attack by water.