Xylan-specific carbohydrate-binding module belonging to family 6 enhances the catalytic performance of a GH11 endo-xylanase
Xylan-specific carbohydrate-binding module belonging to family 6 enhances the catalytic performance of a GH11 endo-xylanase
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DOI：
10.1016/j.nbt.2016.02.006
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发表时间：
2016-06-25
影响因子：
5.4
通讯作者：
Ruller, Roberto
中科院分区：
文献类型：
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作者：
Hoffmam, Zaira B.;Zanphorlin, Leticia M.;Ruller, Roberto
木聚糖酶催化从木聚糖链中水解β-1，4-连接的木糖基，木聚糖链是植物细胞壁中含量最丰富的半纤维素多糖之一。这些酶既可以作为单一的催化域存在，也可以作为由一个或多个附加在催化核心上的碳水化合物结合模块(CBM)组成的模块化蛋白质存在。然而，催化结构域与其CBM之间的协同作用的分子机制还不完全清楚。因此，这项研究的目的是评估属于家族6的煤层气与来自枯草杆菌的GH11木聚糖酶融合的功能效应，该煤层气对木聚糖具有高亲和力，而枯草芽孢杆菌没有野生型煤层气。在大肠杆菌中异源表达野生型酶(BsXyl11)和嵌合蛋白(BsXyl11-CBM6)，纯化后用于生化鉴定。分子融合没有改变对pH和温度的依赖性，但动力学数据显示嵌合酶的催化效率提高了65%。此外，将BsXyl11-CBM6嵌合体添加到商品鸡尾酒Accellerase(R)1500中，使处理后的蔗渣还原糖释放量提高了17%。这些结果表明，CBM6可以作为一种分子工具来提高内切木聚糖酶(GH11)的催化性能，并为开发优化的生物技术应用生物催化剂提供了一种新的策略。
Xylanases catalyze the hydrolysis of beta-1,4-linked xylosyl moieties from xylan chains, one of the most abundant hemicellulosic polysaccharides found in plant cell walls. These enzymes can exist either as single catalytic domains or as modular proteins composed of one or more carbohydrate-binding modules (CBMs) appended to the catalytic core. However, the molecular mechanisms governing the synergistic effects between catalytic domains and their CBMs are not fully understood. Thus, the goal of this study was to evaluate the functional effects of the fusion of a CBM belonging to family 6, which exhibits high affinity to xylan, with the GH11 xylanase from Bacillus subtilis, which does not have a CBM in its wild-type form. The wild-type enzyme (BsXyl11) and the chimeric protein (BsXyl11-CBM6) were heterologously produced in Escherichia coli and purified to homogeneity for biochemical characterization. The molecular fusion did not alter the pH and temperature dependence, but kinetic data revealed an increase of 65% in the catalytic efficiency of the chimeric enzyme. Furthermore, the BsXyl11-CBM6 chimera was used to supplement the commercial cocktail Accellerase (R) 1500 and improved the reducing sugar release by 17% from pretreated sugarcane bagasse. These results indicate that CBM6 can be used as a molecular tool to enhance the catalytic performance of endo-xylanases (GH11) and provide a new strategy for the development of optimized biocatalysts for biotechnological applications.