Abstract：
Xylanase is the most important hydrolase in the xylan hydrolase system, the main function of which is β-1,4-endo-xylanase, which randomly cleaves xylans to xylo-oligosaccharides and xylose. Xylanase has wide ranging of applications, but there remains little research on the cold-adapted enzymes required in some low-temperature industries. Glycoside hydrolase family 8 (GH8) xylanases have been reported to have cold-adapted enzyme activity. In this study, the xylanase gene dgeoxyn was excavated from Deinococcus geothermalis through sequence alignment. The recombinant xylanase DgeoXyn encodes 403 amino acids with a theoretical molecular weight of 45.39 kDa. Structural analysis showed that DgeoXyn has a (α/α)6-barrel fold structure typical of GH8 xylanase. At the same time, it has strict substrate specificity, is only active against xylan, and its hydrolysis products include xylobiose, xylotrinose, xytetranose, xylenanose, and a small amount of xylose. DgeoXyn is most active at 70 ℃ and pH 6.0. It is very stable at 10, 20, and 30 ℃, retaining more than 80% of its maximum enzyme activity. The enzyme activity of DgeoXyn increased by 10% after the addition of Mn2+ and decreased by 80% after the addition of Cu2+. The Km and Vmax of dgeox were 42 mg/ml and 20,000 U/mg, respectively, at a temperature of 70 ℃ and pH of 6.0 using 10 mg/ml beechwood xylan as the substrate. This research on DgeoXyn will provide a theoretical basis for the development and application of low-temperature xylanase.
摘要：
木聚糖酶是木聚糖水解酶体系中最重要的水解酶，其主要功能是β-1,4-内切木聚糖酶，将木聚糖随机裂解为低聚木糖和木糖。木聚糖酶具有广泛的应用,但是对一些低温行业所需的冷适应酶的研究很少。据报道,糖苷水解酶家族8(GH8)木聚糖酶具有冷适应酶活性。在这项研究中,通过序列比对，从地热异常球菌中挖掘了木聚糖酶基因dgeoxyn。重组木聚糖酶DgeoXyn编码403个氨基酸，理论分子量为45.39kDa。结构分析表明，DgeoXyn具有典型的GH8木聚糖酶的（α/α）6桶折叠结构。同时,它具有严格的底物特异性，只对木聚糖有活性,其水解产物包括木二糖，木甲糖,木糖,二甲苯糖,和少量的木糖。DgeoXyn在70℃和pH6.0时最活跃。它在10、20和30℃下非常稳定，保留其最大酶活性的80％以上。DgeoXyn的酶活性在添加Mn2+后增加了10%，在添加Cu2+后降低了80%。dgeox的Km和Vmax分别为42mg/ml和20,000U/mg，分别,在温度为70℃和pH为6.0的条件下，使用10mg/ml山毛鱼木聚糖作为底物。本研究为低温木聚糖酶的开发和应用提供了理论依据。
