N13D、S40E点突变提高木聚糖酶XYNB的热稳定性

Site-directed Mutagenesis of N13D、S40E Improved the Thermostability of Xylanase XYNB

摘要:

对来源于Streptomyces olivaceoviridis 的高比活木聚糖酶XYNB进行同源建模和序列比较，设计了N13D、S40E 的定点突变，以期改善中温酶XYNB的热稳定性。突变酶N13D、S40E分别在毕赤酵母中表达，经纯化后与野生型酶XYNB(同样经毕赤酵母表达后纯化)进行酶学性质比较，结果表明，突变酶N13D和S40E在70℃处理5min，热稳定性比XYNB分别提高了24.76%和14.46%；突变酶N13D的比活性比XYNB提高了22%。在其他性质方面突变酶N13D、S40E与野生型酶XYNB基本相似。通过对木聚糖酶XYNB的定点突变，提高了该酶的热稳定性，并为结构与功能的进一步研究提供了材料。

Abstract:

The predicted structure of Streptomyces olivaceoviridis xylanase XYNB was made by homology modeling and BLAST. Then N13D and S40E mutations were introduced into wide-type XYNB separately by site-directed mutagenesis to improve the enzyme thermostability. XYNB and the mutants (N13D、S40E) were expressed in Pichia pastoris and purified. Their enzymatic properties were determined. The result revealed that the thermostability of N13D and S40E were improved by 24.76% and 14.46% respectively compared with XYNB at 70℃ for 5 min. The specific activity of N13D was increased by 22% compared with XYNB. The other enzymatic properties of mutants were similar to XYNB. The mutants N13D and S40E are good materials for further research in the relationship between structure and function of xylanase XYNB.