Yang Hao-Meng, Yao Bin, Luo Hui-Ying, Zhang Wang-Zhao, Wang Ya-Ru, Yuan Tie-Zheng, Bai Ying-Guo, Wu Ning-Feng, Fan Yun-Liu
Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
Sheng Wu Gong Cheng Xue Bao. 2005 May;21(3):414-9.
A homology modeling of xylanase XYNB from Streptomyces olivaceoviridis A1 was made by Swiss-Model. The hydrophobic Interaction between beta-sheet B1 and B2 in the tertiary structure model of XYNB was compared with other thermophilic xylanase. A T11Y mutation was introduced in XYNB by site-dirrected mutagenesis to improve the thermostability of the enzyme. The XYNB and mutant xylanase (XYNB') expressed in Pichia pastoris were purified and their enzymatic properties were determined. The result revealed that the thermostability of XYNB' was obviously higher than that of XYNB. The optimal temperature of XYNB' for its activity was 60 degrees C, similar to XYNB. But, compare to XYNB, the optimal pH value, the Km value and the specific activity of XYNB' had also been changed. The research results suggested that the aromatic interaction between beta-sheet B1 and B2 in xylanase should increase enzyme thermostability. The mutant xylanase XYNB' is a good material for further research in the relationship between structure and function of xylanase.
通过瑞士模型对橄榄绿链霉菌A1的木聚糖酶XYNB进行了同源建模。将XYNB三级结构模型中β-折叠B1和B2之间的疏水相互作用与其他嗜热木聚糖酶进行了比较。通过定点诱变在XYNB中引入T11Y突变以提高该酶的热稳定性。对在毕赤酵母中表达的XYNB和突变木聚糖酶（XYNB'）进行了纯化，并测定了它们的酶学性质。结果表明，XYNB'的热稳定性明显高于XYNB。XYNB'的最佳活性温度为60℃，与XYNB相似。但是，与XYNB相比，XYNB'的最佳pH值、Km值和比活性也发生了变化。研究结果表明，木聚糖酶中β-折叠B1和B2之间的芳香族相互作用应会提高酶的热稳定性。突变木聚糖酶XYNB'是进一步研究木聚糖酶结构与功能关系的良好材料。
