Shi Pengjun, Du Yanlong, Yang Hong, Huang Huoqing, Zhang Xiu, Wang Yaru, Yao Bin
Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
College of Biological Science and Engineering, Bei Fang University of Nationalities, Yinchuan 750021, China.
Biomed Res Int. 2015;2015:149504. doi: 10.1155/2015/149504. Epub 2015 Jan 5.
An endo-1,4-β-xylanase-encoding gene, xyn11B, was cloned from the thermophilic fungus Humicola insolens Y1. The gene encodes a multimodular xylanase that consists of a typical hydrophobic signal sequence, a catalytic domain of glycoside hydrolase (GH) family 11, a glycine-rich linker, and a family 1 carbohydrate binding module (CBM1). Deduced Xyn11B shares the highest identity of 74% with a putative xylanase from Podospora anserina S mat+. Recombinant Xyn11B was successfully expressed in Pichia pastoris and purified to electrophoretic homogeneity. Xyn11B had a high specific activity of 382.0 U mg(-1) towards beechwood xylan and showed optimal activity at pH 6.0 and 50°C. Distinct from most reported acidic fungal xylanases, Xyn11B was alkaline-tolerant, retaining 30.7% of the maximal activity at pH 9.0. The K m and V max values for beechwood xylan were 2.2 mg mL(-1) and 462.8 μmol min(-1) mg(-1), respectively. The enzyme exhibited a wider substrate specificity and produced a mixture of xylooligosaccharides. All these favorable enzymatic properties make Xyn11B attractive for potential applications in various industries.
从嗜热真菌特异腐质霉Y1中克隆到一个编码内切-1,4-β-木聚糖酶的基因xyn11B。该基因编码一种多模块木聚糖酶，其包含一个典型的疏水信号序列、一个糖苷水解酶（GH）家族11的催化结构域、一个富含甘氨酸的连接子和一个家族1碳水化合物结合模块（CBM1）。推导的Xyn11B与来自栗疫菌S mat+的一种假定木聚糖酶具有74%的最高同一性。重组Xyn11B在毕赤酵母中成功表达并纯化至电泳纯。Xyn11B对山毛榉木聚糖具有382.0 U mg-1的高比活性，在pH 6.0和50°C时表现出最佳活性。与大多数已报道的酸性真菌木聚糖酶不同，Xyn11B耐碱性，在pH 9.0时保留最大活性的30.7%。山毛榉木聚糖的Km和Vmax值分别为2.2 mg mL-1和462.8 μmol min-1 mg-1。该酶表现出更广泛的底物特异性，并产生低聚木糖混合物。所有这些有利的酶学性质使得Xyn11B在各种工业潜在应用中具有吸引力。
