Wang Guozeng, Wu Jingjing, Yan Renxiang, Lin Juan, Ye Xiuyun
Fujian Key Laboratory of Marine Enzyme Engineering, Fuzhou UniversityFuzhou, China; College of Biological Science and Technology, Fuzhou UniversityFuzhou, China.
College of Biological Science and Technology, Fuzhou University Fuzhou, China.
Front Microbiol. 2017 Jan 4;7:2120. doi: 10.3389/fmicb.2016.02120. eCollection 2016.
A novel multi-domain high molecular xylanase coding gene () was cloned from sp. SL3, an alkaliphilic bacterial strain isolated from the sediment of soda lake Dabusu. The deduced XynSL3 is composed of a putative signal peptide, three tandem domains of carbohydrate binding module (CBM) family 22, a catalytic domain of glycosyl hydrolase (GH) family 10 and a domain of CBM9. XynSL3 shares the highest identity of 66% to a hypothetical protein from sp. AK22 and has low identities (33-45%) with other functionally characterized xylanases. The gene was expressed heterologously in and the recombinant enzyme demonstrated some particular characteristics. Purified recombinant XynSL3 (rXynSL3) was highly active and stable over the neutral and alkaline pH ranges from 7.0 to 12.0, with maximum activity at pH 9.0 and around 45% activity at pH 12.0. It had an apparent temperature optimum of 55°C and was stable at 50°C. The rXynSL3 was highly halotolerant, retaining more than 60% activity with 3 M NaCl and was stable at up to a 4 M concentration of NaCl. The hydrolysis products of rXynSL3 from corncob xylan were mainly xylobiose and xylotetraose. The activity of rXynSL3 was enhanced by Ca and it has strong resistance to sodium dodecyl sulfate (SDS). This multi-domain, alkaline and salt-tolerant enzyme has great potential for basic research and industrial applications such as the biobleaching of paper pulp and production of xylo-oligosaccharides (XOS).
从大布苏苏打湖沉积物中分离得到的嗜碱菌株芽孢杆菌属sp. SL3中克隆出一个新型多结构域高分子木聚糖酶编码基因（）。推导的XynSL3由一个假定的信号肽、碳水化合物结合模块（CBM）家族22的三个串联结构域、糖基水解酶（GH）家族10的催化结构域和CBM9结构域组成。XynSL3与芽孢杆菌属sp. AK22的一种假定蛋白具有66%的最高同源性，与其他功能已明确的木聚糖酶具有较低的同源性（33 - 45%）。该基因在中进行了异源表达，重组酶表现出一些特殊特性。纯化的重组XynSL3（rXynSL3）在7.0至12.0的中性和碱性pH范围内具有高活性和稳定性，在pH 9.0时活性最高，在pH 12.0时约有45%的活性。其最适温度明显为55°C，在50°C时稳定。rXynSL3具有高度耐盐性，在3 M NaCl存在下保留超过60%的活性，在高达4 M的NaCl浓度下仍稳定。rXynSL3对玉米芯木聚糖的水解产物主要是木二糖和木四糖。rXynSL3的活性受到Ca的增强，并且对十二烷基硫酸钠（SDS）具有很强的抗性。这种多结构域、碱性和耐盐的酶在基础研究和工业应用（如纸浆生物漂白和木寡糖（XOS）生产）方面具有巨大潜力。
