Mutation of non-conserved amino acids surrounding catalytic site to shift pH optimum of Bacillus circulans xylanase
Mutation of non-conserved amino acids surrounding catalytic site to shift pH optimum of Bacillus circulans xylanase
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DOI：
10.1016/j.molcatb.2008.02.006
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发表时间：
2008-11-01
影响因子：
--
通讯作者：
Yoo, Young Je
中科院分区：
文献类型：
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作者：
Kim, Seok Hwan;Pokhrel, Subarna;Yoo, Young Je
通过工程改造提高酶活性的pH依赖性对环状芽孢杆菌木聚糖酶的工业应用具有重要意义。通过B之间的结构比对选择靶突变位点。环状木聚糖酶和其它具有不同最适pH的木聚糖酶。我们从催化残基中选择了8 A内的非保守突变位点，以观察这些残基是否在调节催化残基的pK（a）s中具有某种作用。我们推测，在酶催化中可能没有任何作用的非保守残基可能会干扰催化残基的pK（a）s。计算由于突变的静电势的变化而引起的可滴定基团的pK（a）s的变化，并根据催化残基的pK（a）的变化预测最适pH的变化。我们的策略被证明是有用的，在选择有前途的突变体转移的木聚糖酶的最适pH值向所需的一侧。(c)2008 Elsevier B.V.保留所有权利。
Improvement of enzyme function by engineering pH dependence of enzymatic activity is of importance for industrial application of Bacillus circulans xylanases. Target mutation sites were selected by structural alignment between B. circulans xylanase and other xylanases having different pH optima. We selected non-conserved mutant sites within 8 A from the catalytic residues, to see whether these residues have some role in modulating pK(a)s of the catalytic residues. We hypothesized that the non-conserved residues which may not have any role in enzyme catalysis might perturb pK(a)s of the catalytic residues. Change in pK(a)s of a titratable group due to change in electrostatic potential of a mutation was calculated and the change in pH optimum was predicted from the change in pK(a) of the catalytic residues. Our strategy is proved to be useful in selection of promising mutants to shift the pH optimum of the xylanases towards desired side. (c) 2008 Elsevier B.V. All rights reserved.