二硫键影响GH11木聚糖酶稳定性研究进展

低聚木糖具有改善肠道微生态的益生作用,在降血糖、降血压、防止便秘等方面表现出良好的保健效果。近年来,利用生物酶技术制备功能性低聚木糖的相关研究受到广泛关注。糖苷水解酶(glycoside hydrolase, GH)11家族木聚糖酶具有底物特异性强和催化效率高的特点,在低聚木糖生产应用中表现出显著优势；然而,大多数天然GH11木聚糖酶存在稳定性较差的问题,无法满足工业生产中高温、酸、碱等极端条件的要求。利用酶工程技术对天然木聚糖酶进行分子改造,以适应高温、酸、碱等生产条件,使底物特异性强、催化效率高的酶相对稳定地发挥作用,对于制备功能性低聚木糖的工业生产具有重要的实际意义。根据GH11木聚糖酶的分子结构及其特点,通过比较其分子内相互作用力对酶热稳定性的影响,发现二硫键在改善酶的稳定性方面具有十分显著的优势。基于对GH11木聚糖酶结构的分析,总结了引入二硫键的常规策略,比较了酶在不同区域引入不同数量二硫键对GH11木聚糖酶稳定性的改善效果,对引入二硫键后酶稳定性显著变化的几个区域进行定位,并指出多个二硫键对改善酶稳定性的作用方式,希望为提高酶稳定性的酶分子改造研究提供基础数据,为拓宽GH11木聚糖酶工业应用范围提供科学参考。

Research Progress on Effect of Constructing Disulfide Bond on Stability of Glycoside Hydrolase 11 Xylanase

Xylooligosaccharides have shown good prebiotic effects in improving intestinal microecology,and good health care effects in lowering blood glucose, blood pressure, and preventing constipation and so on. In recent years, studies on the preparation of functional xylooligosaccharides using bioenzyme technology have attracted much attention. The features of high specificity and catalytic efficiency of the glycoside hydrolase (GH) 11 xylanase had obvious advantages for xylooligosaccharide production. However, poor stability of most natural GH11 xylanase made it unable to meet the requirements of extreme conditions such as high temperature, strong acid and alkali in industrial production. Molecular modification of natural xylanase by enzyme engineering technology could make xylanase with good substrate specificity and high catalytic efficiency applicable to extreme industrial conditions such as high temperature, strong acid and alkali,which was important and practical for the industrial production of functional xylooligosaccharides. According to the molecular structure of the GH11 xylanase and its characteristics, disulfide bonds have been found to be of great advantage in improving the stability of the enzyme by comparing their intramolecular interaction forces on the thermal stability of the enzyme. Based on the analysis of the structure of the GH11 xylanase, the common strategies for constructing disulfide bonds was summarized, and the effects of constructing single or multiple disulfide bonds in different regions of the enzyme on improving the stability of the GH11 xylanase were compared. Several regions that showed significant changes in enzyme stability after construction of disulfide bonds were localized, and the mode of action of multiple disulfide bonds on improving enzyme stability was introduced. It was expected to provide valuable information for relevant studies on the improvement of stability by enzyme molecular modification, and to broaden the range of industrial applications of GH11 xylanase.