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首页> 外文期刊>Journal of Molecular Biology >A family 10 Thermoascus aurantiacus xylanase utilizes arabinose decorations of xylan as significant substrate specificity determinants
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A family 10 Thermoascus aurantiacus xylanase utilizes arabinose decorations of xylan as significant substrate specificity determinants

机译：家族的10嗜热性色霉木聚糖酶利用木聚糖的阿拉伯糖装饰作为重要的底物特异性决定因素

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摘要

Xylan, which is a key component of the plant cell wall, consists of a backbone of beta-1,4-linked xylose residues that are decorated with arabinofuranose, acetyl, 4-O-methyl D-glucuronic acid and ferulate. The backbone of xylan is hydrolysed by endo-beta 1,4-xylanases (xylanases); however, it is unclear whether the various side-chains of the polysaccharide are utilized by these enzymes as significant substrate specificity determinants. To address this question we have determined the crystal structure of a family 10 xylanase from Thermoascus aurantiacus, in complex with xylobiose containing an arabinofuranosyl-ferulate side-chain. We show that the distal glycone subsite of the enzyme makes extensive direct and indirect interactions with the arabinose side-chain, while the ferulate moiety is solvent-exposed. Consistent with the 3D structural data, the xylanase displays fourfold more activity against xylotriose in which the non-reducing moiety is linked to an arabinose side-chain, compared to the undecorated form of the oligosacchairde. These data indicate that the sugar decorations of xylans in the T. aurantiacus family 10 xylanase, rather than simply being accommodated, can be significant substrate specificity determinants. (c) 2005 Elsevier Ltd. All rights reserved.
机译：木聚糖是植物细胞壁的关键成分，由β-1,4-连接的木糖残基的骨架组成，该残基用阿拉伯呋喃糖，乙酰基，4-O-甲基D-葡萄糖醛酸和阿魏酸修饰。木聚糖的骨架被内切β1,4-木聚糖酶（木聚糖酶）水解;然而，尚不清楚这些酶是否将多糖的各种侧链用作重要的底物特异性决定因素。为了解决这个问题，我们确定了来自澳大利亚古猿嗜热菌的10族木聚糖酶的晶体结构，并与含有阿拉伯呋喃糖基-阿魏酸酯侧链的木糖复合。我们表明，该酶的远端糖基亚位点与阿拉伯糖侧链进行广泛的直接和间接相互作用，而阿魏酸部分则被溶剂暴露。与3D结构数据一致，与寡糖形式的未修饰形式相比，木聚糖酶显示出更高的针对木糖三糖的活性，其中木糖的非还原部分与阿拉伯糖侧链相连。这些数据表明，而不是简单地容纳，而是将奥氏酵母（T. aurantiacus）10木聚糖酶中的木聚糖的糖修饰作为重要的底物特异性决定因素。 （c）2005 Elsevier Ltd.保留所有权利。

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