Functional diversity of family 3 beta-glucosidases from thermophilic cellulolytic fungus Humicola insolens Y1

文献类型： 外文期刊

第一作者： Xia, Wei

作者： Xia, Wei;Qian, Lichun;Zhan, Xiuan;Xia, Wei;Bai, Yingguo;Cui, Ying;Shi, Pengjun;Luo, Huiying;Yao, Bin;Xu, Xinxin;Zhang, Wei

作者机构：

期刊名称：SCIENTIFIC REPORTS （ 影响因子：4.379； 五年影响因子：5.133 ）

ISSN： 2045-2322

年卷期： 2016 年 6 卷

页码：

收录情况： SCI

摘要： The fungus Humicola insolens is one of the most powerful decomposers of crystalline cellulose. However, studies on the beta-glucosidases from this fungus remain insufficient, especially on glycosyl hydrolase family 3 enzymes. In the present study, we analyzed the functional diversity of three distant family 3 beta-glucosidases from Humicola insolens strain Y1, which belonged to different evolutionary clades, by heterogeneous expression in Pichia pastoris strain GS115. The recombinant enzymes shared similar enzymatic properties including thermophilic and neutral optima (50-60 degrees C and pH 5.5-6.0) and high glucose tolerance, but differed in substrate specificities and kinetics. HiBgl3B was solely active towards aryl beta-glucosides while HiBgl3A and HiBgl3C showed broad substrate specificities including both disaccharides and aryl beta-glucosides. Of the three enzymes, HiBgl3C exhibited the highest specific activity (158.8 U/mg on pNPG and 56.4 U/mg on cellobiose) and catalytic efficiency and had the capacity to promote cellulose degradation. Substitutions of three key residues Ile48, Ile278 and Thr484 of HiBgl3B to the corresponding residues of HiBgl3A conferred the enzyme activity towards sophorose, and vice versa. This study reveals the functional diversity of GH3 beta-g lucosidases as well as the key residues in recognizing +1 subsite of different substrates.

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