A novel glucuronoyl esterase from Aspergillus fumigatus-the role of conserved Lys residue in the preference for 4-O-methyl glucuronoyl esters
A novel glucuronoyl esterase from Aspergillus fumigatus-the role of conserved Lys residue in the preference for 4-O-methyl glucuronoyl esters
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DOI：
10.1007/s00253-018-8739-5
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发表时间：
2018-03-01
影响因子：
5
通讯作者：
Arioka, Manabu
中科院分区：
文献类型：
--
作者：
Huynh, Hung Hiep;Ishii, Nozomi;Arioka, Manabu
植物细胞壁中的纤维素主要由半纤维素和木质素覆盖，因此有效去除这些成分被认为是优化利用木质纤维素的关键步骤。最近发现的碳水化合物酯酶（CE） 15家族葡萄糖醛酸酯酶（GEs）可以切断半纤维素中d-葡萄糖醛酸的游离羧基和木质素残基中的苯基之间的联系，这可能有助于这一过程。在此，我们报道了从丝状真菌烟曲霉（Aspergillus fumigatus）中提取的GE （AfGE）的鉴定、功能表达和酶学特性。AfGE在米曲霉中异种表达，纯化后的酶具有降解模拟半纤维素和木质素之间酯链的合成底物的能力。AfGE是一种具有潜在工业应用价值的酶，因为它是一种嗜热酶，在pH值为5时的有利温度为40-50℃。AfGE的分子建模和定点诱变研究表明，Lys209在对葡萄糖醛酸环中含有4- o -甲基的底物的偏好中起重要作用。
Cellulose in plant cell walls is mainly covered by hemicellulose and lignin, and thus efficient removal of these components is thought to be a key step in the optimal utilization of lignocellulose. The recently discovered carbohydrate esterase (CE) 15 family of glucuronoyl esterases (GEs) which cleave the linkages between the free carboxyl group of d-glucuronic acid in hemicellulose and the benzyl groups in lignin residues could contribute to this process. Herein, we report the identification, functional expression, and enzymatic characterization of a GE, AfGE, from the filamentous fungus Aspergillus fumigatus. AfGE was heterologously expressed in Aspergillus oryzae, and the purified enzyme displayed the ability to degrade the synthetic substrates mimicking the ester linkage between hemicellulose and lignin. AfGE is a potentially industrially applicable enzyme due to its characteristic as a thermophilic enzyme with the favorable temperature of 40-50 A degrees C at pH 5. Molecular modeling and site-directed mutagenesis studies of AfGE demonstrated that Lys209 plays an important role in the preference for the substrates containing 4-O-methyl group in the glucopyranose ring.