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首页> 外文期刊>Journal of bacteriology >Domain Analysis of a Modular α-l-Arabinofuranosidase with a Unique Carbohydrate Binding Strategy from the Fiber-Degrading Bacterium Fibrobacter succinogenes S85
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Domain Analysis of a Modular α-l-Arabinofuranosidase with a Unique Carbohydrate Binding Strategy from the Fiber-Degrading Bacterium Fibrobacter succinogenes S85

机译：具有独特的碳水化合物结合策略的纤维降解细菌琥珀酸纤维杆菌S85的模块化α-1-阿拉伯呋喃糖苷酶的域分析

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摘要

Family 43 glycoside hydrolases (GH43s) are known to exhibit various activities involved in hemicellulose hydrolysis. Thus, these enzymes contribute to efficient plant cell wall degradation, a topic of much interest for biofuel production. In this study, we characterized a unique GH43 protein from Fibrobacter succinogenes S85. The recombinant protein showed α-l-arabinofuranosidase activity, specifically with arabinoxylan. The enzyme is, therefore, an arabinoxylan arabinofuranohydrolase (AXH). The F. succinogenes AXH (FSUAXH1) is a modular protein that is composed of a signal peptide, a GH43 catalytic module, a unique β-sandwich module (XX domain), a family 6 carbohydrate-binding module (CBM6), and F. succinogenes-specific paralogous module 1 (FPm-1). Truncational analysis and site-directed mutagenesis of the protein revealed that the GH43 domain/XX domain constitute a new form of carbohydrate-binding module and that residue Y484 in the XX domain is essential for binding to arabinoxylan, although protein structural analyses may be required to confirm some of the observations. Kinetic studies demonstrated that the Y484A mutation leads to a higher kcat for a truncated derivative of FSUAXH1 composed of only the GH43 catalytic module and the XX domain. However, an increase in the Km for arabinoxylan led to a 3-fold decrease in catalytic efficiency. Based on the knowledge that most XX domains are found only in GH43 proteins, the evolutionary relationships within the GH43 family were investigated. These analyses showed that in GH43 members with a XX domain, the two modules have coevolved and that the length of a loop within the XX domain may serve as an important determinant of substrate specificity.
机译：已知43族糖苷水解酶（GH43s）表现出参与半纤维素水解的各种活性。因此，这些酶有助于有效的植物细胞壁降解，这是生物燃料生产中非常感兴趣的话题。在这项研究中，我们表征了来自 Fibrobacter succinogenes S85的独特GH43蛋白。重组蛋白显示出α-1-阿拉伯呋喃糖苷酶活性，特别是具有阿拉伯木聚糖。因此，该酶是阿拉伯木聚糖阿拉伯呋喃糖水解酶（AXH）。 F。琥珀酸（Succinogenes） AXH（FSUAXH1）是一种模块化蛋白，由信号肽，GH43催化模块，独特的β三明治模块（XX结构域），6族碳水化合物结合模块（CBM6）和< em> F。琥珀酸特异的同源模块1（FPm-1）。蛋白质的截断分析和定点诱变显示GH43结构域/ XX结构域构成了碳水化合物结合模块的新形式，并且XX结构域中的残基Y484是与阿拉伯木聚糖结合所必需的，尽管蛋白质结构分析可能需要确认一些观察结果。动力学研究表明，对于仅由GH43催化模块和XX结构域组成的FSUAXH1截短衍生物，Y484A突变导致更高的 k cat 。但是，阿拉伯木聚糖的 K m 的增加导致催化效率降低了3倍。基于仅在GH43蛋白中发现大多数XX结构域的知识，研究了GH43家族内的进化关系。这些分析表明，在具有XX域的GH43成员中，两个模块共同进化，并且XX域内环的长度可能是底物特异性的重要决定因素。

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