Catalytic mechanism of limonene epoxide hydrolase, a theoretical study
Catalytic mechanism of limonene epoxide hydrolase, a theoretical study
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DOI：
10.1021/ja050940p
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发表时间：
2005-10-19
影响因子：
15
通讯作者：
Himo, F
中科院分区：
文献类型：
--
作者：
Hopmann, KH;Hallberg, BM;Himo, F
采用密度泛函方法B3LYP对环氧化柠檬烯水解酶（LEH）的催化机理进行了理论研究。LEH是红红红球菌DCL14中发现的一种新的柠檬烯降解途径的一部分，它催化柠檬烯-1,2-环氧化物水解生成柠檬烯-1,2-二醇。利用LEH的最新晶体结构，建立了由5个氨基酸和一个晶体学观察到的水分子组成的LEH活性位点模型。用该模型对不同底物的水解进行了研究。结果表明，LEH采用了一种通用酸/通用碱催化的反应机制，包括Asp101使底物质子化，水对环氧化物的亲核攻击，Asp132从水中提取质子。此外，我们对实验观察到的柠檬烯-1,2-环氧化物的四个立体异构体的区域选择性水解提供了解释。
The catalytic mechanism of limonene epoxide hydrolase (LEH) was investigated theoretically using the density functional theory method B3LYP. LEH is part of a novel limonene degradation pathway found in Rhodococcus erythropolis DCL14, where it catalyzes the hydrolysis of limonene-1,2-epoxide to give limonene-1,2-diol. The recent crystal structure of LEH was used to build a model of the LEH active site composed of five amino acids and a crystallographically observed water molecule. With this model, hydrolysis of different substrates was investigated. It is concluded that LEH employs a concerted general acid/general base-catalyzed reaction mechanism involving protonation of the substrate by Asp101, nucleophilic attack by water on the epoxide, and abstraction of a proton from water by Asp132. Furthermore, we provide an explanation for the experimentally observed regioselective hydrolysis of the four stereoisomers of limonene-1,2-epoxide.