Importance of the carbohydrate-binding module of Clostridium stercorarium Xyn10B to xylan hydrolysis
Importance of the carbohydrate-binding module of Clostridium stercorarium Xyn10B to xylan hydrolysis
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DOI：
10.1271/bbb.65.41
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发表时间：
2001-01-01
影响因子：
1.6
通讯作者：
Ohmiya, K
中科院分区：
文献类型：
--
作者：
Ali, MK;Hayashi, H;Ohmiya, K
粪梭菌木聚糖酶XynlOB是模块化酶，其包含两个热稳定结构域、糖基水解酶的家族10催化结构域、家族9碳水化合物结合模块（CBM）和两个S层同源（SLH）结构域[Biosci，Biotechnol.，63，1596-1604（1999）]。为了研究这种CBM的作用，我们构建了Xyn 10 B的两个衍生物，并比较了它们对木聚糖和植物细胞壁的一些制备物的水解活性; Xyn 10 B Delta CBM仅由催化结构域组成，Xyn 10 B-CBM包括催化结构域和CBM。Xyn 10 B-CBM与各种不溶性多糖结合，包括Avicel、酸溶胀纤维素、球磨几丁质、Sephadex G-25和直链淀粉树脂。在可溶性淀粉存在下的纤维素结合测定表明，Xyn 10 B的CBM甚至对单糖如葡萄糖、半乳糖、木糖、甘露糖和核糖具有亲和力，从酶中去除CBM否定了其纤维素和木聚糖结合能力，并严重降低了其对不溶性木聚糖和植物细胞壁的酶活性，但不可溶性木聚糖。这些发现清楚地表明Xyn 10 B的CBM在不溶性木聚糖的水解中是重要的。这是第一次报告的家庭9 CBM与不溶性木聚糖的亲和力，除了结晶纤维素和能力，以增加对不溶性木聚糖的水解活性。
The Clostridium stercorarium xylanase Xyn10B is a modular enzyme comprising two thermostabilizing domains, a family 10 catalytic domain of glycosyl hydrolases, a family 9 carbohydrate-binding module (CBM), and two S-layer homologous (SLH) domains [Biosci, Biotechnol. Biochem,, 63, 1596-1604 (1999)]. To investigate the role of this CBM, we constructed two derivatives of Xyn10B and compared their hydrolytic activity toward xylan and some preparations of plant cell walls; Xyn10B Delta CBM consists of a catalytic domain only, and Xyn10B-CBM comprises a catalytic domain and a CBM. Xyn10B-CBM bound to various insoluble polysaccharides including Avicel, acid-swollen cellulose, ball-milled chitin, Sephadex G-25, and amyloseresin, A cellulose binding assay in the presence of soluble saccharides suggested that the CBM of Xyn10B had an affinity for even monosaccharides such as glucose, galactose, xylose, mannose and ribose, Removal of the CBM from the enzyme negated its cellulose- and xylan-binding abilities and severely reduced its enzyme activity toward insoluble xylan and plant cell walls but not soluble xylan. These findings clearly indicated that the CBM of Xyn10B is important in the hydrolysis of insoluble xylan. This is the first report of a family 9 CBM with an affinity for insoluble xylan in addition to crystalline cellulose and the ability to increase hydrolytic activity toward insoluble xylan.