Thermostabilization of extremophilic Dictyoglomus thermophilum GH11 xylanase by an N-terminal disulfide bridge and the effect of ionic liquid [emim]OAc on the enzymatic performance

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• 作者：He Li ; Anna Kankaanp盲盲 ; Hairong Xiong ; Michael Hummel ; Herbert Sixta ; Heikki Ojamo ; Ossi Turunen
• 关键词：GH11 xylanase ; Dictyoglomus thermophilum ; N-terminal disulphide bridge ; Thermostability ; Ionic liquid ; [emim]OAc
• 刊名：Enzyme and Microbial Technology
• 出版年：10 December, 2013
• 年：2013
• 卷：53
• 期：6-7
• 页码：414-419
• 全文大小：1020 K

文摘

In the present study, an extremophilic GH11 xylanase was stabilized by an engineered N-terminal disulphide bridge. The effect of the stabilization was then tested against high temperatures and in the presence of a biomass-dissolving ionic liquid, 1-ethyl-3-methylimidazolium acetate ([emim]OAc). The N-terminal disulfide bridge increased the half-life of a GH11 xylanase (XYNB) from the hyperthermophilic bacterium Dictyoglomus thermophilum by 10-fold at 100 掳C. The apparent temperature optimum increased only by 鈭? 掳C, which is less than the corresponding increase in mesophilic (鈭?5 掳C) and moderately thermophilic (鈭?0 掳C) xylanases. The performance of the enzyme was increased significantly at 100-110 掳C. The increasing concentration of [emim]OAc almost linearly increased the inactivation level of the enzyme activity and 25% [emim]OAc inactivated the enzyme almost fully. On the contrary, the apparent temperature optimum did not decrease to a similar extent, and the degree of denaturation of the enzyme was also much lower according to the residual activity assays. Also, 5% [emim]OAc largely counteracted the benefit obtained by the stabilizing disulfide bridge in the temperature-dependent activity assays, but not in the stability assays. K_m was increased in the presence of [emim]OAc, indicating that [emim]OAc interfered the substrate-enzyme interactions. These results indicate that the effect of [emim]OAc is targeted more to the functioning of the enzyme than the basic stability of the hyperthermophilic GH11 xylanase.