Why substituting the asparagine at position 35 in Bacillus circulans xylanase with an aspartic acid remarkably improves the enzymatic catalytic activity? A quantum chemistry-based calculation study
Why substituting the asparagine at position 35 in Bacillus circulans xylanase with an aspartic acid remarkably improves the enzymatic catalytic activity? A quantum chemistry-based calculation study
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为什么用天冬氨酸取代环状芽孢杆菌木聚糖酶中35位的天冬酰胺可以显着提高酶的催化活性？
DOI：
10.1016/j.polymdegradstab.2011.01.010
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发表时间：
2011-05
影响因子：
5.9
通讯作者：
Wang, Lushan
中科院分区：
文献类型：
--
作者：
Li, Jinghua;Wang, Lushan
来自环状芽孢杆菌（Bacillus circulans， BCX）的木聚糖酶是一种构型保持型糖苷水解酶，它以两个谷氨酸残基（Glu78和Glu172）作为催化活性残基，根据双位移机制水解木聚糖。已有实验研究表明，将Glu172旁边35位的天冬酰胺（Asn）突变为天冬氨酸（Asp）可以明显提高BCX的催化活性。为了更好地理解实验发现的内在机制，我们对两个模型系统进行了量子化学计算，以模拟野生型和突变型bxs的催化作用。详细给出了水解反应中中间体和过渡态的几何结构和相对能。研究发现，在野生型模型系统中，Asn35与Glu172通过一个松散的氢键相互作用，而在突变型模型系统中，Asp35与Glu172形成一个非常紧密的氢键。当Asn35被Asp35取代时，其势垒变化范围为98 ~ 65 kJ mol−1，表明Asp35的存在显著降低了水解反应的能量需求。这一结果从理论上解释了为什么单个氨基酸取代会对BCX的催化活性产生重要影响。
Xylanases from Bacillus circulans (BCX) are known as configuration-retaining glycoside hydrolases, which hydrolyze xylans with two glutamic acid residues (Glu78 and Glu172) serving as catalytic active residues according to a double displacement mechanism. Existing experimental researches show that mutating the asparagines (Asn) to aspartic acid (Asp) at position 35 next to Glu172 can obviously improve the catalytic activity of BCX. To better understand the inherent mechanism for the experimental finding, we performed quantum chemistry calculations on two model systems to mimic the catalyses of wild-type and mutant BCXs. Geometrical structures and relative energies of intermediates and transition states involved in the hydrolysis reactions are given in detail. It is found that in the wild-type model system Asn35 interacts with Glu172 via a loose hydrogen bond, while in the mutant model system Asp35 forms a very tight hydrogen bond with Glu172. The glycosidic bond cleavage is proposed to be the rate-determining step for the hydrolysis reaction, whose barrier varies from 98 to 65 kJ mol−1when Asn35 is replaced by Asp35, showing the presence of Asp35 remarkably reduces the energy demand for the hydrolysis reaction. The present result provides a theoretical elucidation for why a single amino acid substitution can importantly influences catalytic activity of BCX.
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影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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DOI：
10.1021/jp045141s
发表时间：
2005-02
期刊：
The journal of physical chemistry. A
影响因子：
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作者：
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通讯作者：
Yan Zhao;Núria González-García;D. Truhlar
影响因子：
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作者：
DAVIES, G;HENRISSAT, B
通讯作者：
HENRISSAT, B