Microbiology and Metabolic Engineering Key Laboratory of Sichuan Province, College of Life Science, Sichuan University, Sichuan, China.
Curr Microbiol. 2011 Jan;62(1):242-8. doi: 10.1007/s00284-010-9697-z. Epub 2010 Jul 1.
Xylanase is one of the most important hemicellulases in industry. However, its low thermostability limits its applications. In this study, one thermostable xylanase-producing strain 400264 was obtained from screening 11 Aspergillus niger strains (producing thermotolerant xylanase), and the optimum temperature of crude xylanase extracted from it was 55°C. Original activity of the crude xylanase is 64% at 60°C and 55% at 85°C with an incubation time of 30 min, respectively. After the expression of recombinant xylanase gene (xynA/xynB), the XYNB (xylanase B) showed higher thermostability than XYNA (xylanase A). Recombinant enzyme XYNB retained 94% of its activity for 10 min at 85°C, while XYNA with no activity left. Site-directed mutagenesis was performed to replace Ala33 of XYNB by Ser33 resulting 19% decrease in enzyme activity after incubating at 85°C for 30 min. It suggested that the Ala33 residue may have a certain effect on the thermophilic adaptation of xylanase.
木聚糖酶是工业中最重要的半纤维素酶之一。然而，其低耐热性限制了它的应用。在这项研究中，从筛选的 11 株黑曲霉（产耐热木聚糖酶）中得到了一株耐热木聚糖酶产生菌 400264，从该菌中提取的粗木聚糖酶的最适温度为 55°C。粗木聚糖酶在 60°C 时的原始活性为 64%，在 85°C 时的原始活性为 55%，孵育时间为 30 min。表达重组木聚糖酶基因（xynA/xynB）后，XYNB（木聚糖酶 B）的耐热性高于 XYNA（木聚糖酶 A）。重组酶 XYNB 在 85°C 下孵育 10 分钟后仍保持 94%的活性，而 XYNA 则没有活性。定点突变将 XYNB 的 Ala33 替换为 Ser33，导致酶在 85°C 下孵育 30 分钟后活性降低 19%。这表明 Ala33 残基可能对半纤维素酶的嗜热适应有一定影响。
