Cellulomonas uda produces Xyn11A, moderately thermostable xylanase, with optimal activity at 50 °C and pH 6.5. An improvement in the biochemical properties of Xyn11A was achieved by site-directed mutagenesis approach. Wild-type xylanase, Xyn11A-WT, and its mutant Xyn11A-N9Y were expressed in Escherichia coli, and then both enzymes were purified and characterized. Xyn11A-N9Y displayed optimal activity at 60 °C and pH 7.5, an upward shift of 10 °C in the optimum temperature and an upward shift of 1 unit in optimum pH; also, it manifested an 11-fold increase in thermal stability at 60 °C, compared to that displayed by Xyn11A-WT. Molecular dynamics simulations of Xyn11A-WT and Xyn11A-N9Y suggest that the substitution N9Y leads to an array of secondary structure changes at the N-terminal end and an increase in the number of hydrogen bonds in Xyn11A-N9Y. Based on the significant improvements, Xyn11A-N9Y may be considered as a candidate for several biotechnological applications.

中文翻译：

---

单突变 N9Y 对纤维单胞菌木聚糖酶 Xyn11A 催化特性的影响：生化和分子动力学模拟分析。

Cellulomonas uda 产生 Xyn11A，中等热稳定性木聚糖酶，在 50 °C 和 pH 6.5 时具有最佳活性。通过定点诱变方法实现了 Xyn11A 生化特性的改进。野生型木聚糖酶 Xyn11A-WT 及其突变体 Xyn11A-N9Y 在大肠杆菌中表达，然后对这两种酶进行纯化和表征。Xyn11A-N9Y在60°C和pH 7.5时表现出最佳活性，最适温度上移10°C，最适pH上移1个单位；此外，与 Xyn11A-WT 相比，它在 60°C 时的热稳定性提高了 11 倍。Xyn11A-WT 和 Xyn11A-N9Y 的分子动力学模拟表明，取代 N9Y 导致 N 末端的一系列二级结构变化和 Xyn11A-N9Y 中氢键数量的增加。