肝醇脱氢酶催化乙醇氧化生成乙醛反应机理的理论研究

Theoretical Study on the Mechanism of Ethanol Oxidation to Acetaldehyde Catalyzed by Liver Alcohol Dehydrogenase

采用B3LYP方法研究了肝醇脱氢酶催化烟酰胺腺嘌呤二核苷酸氧化乙醇生成乙醛的反应机理.优化得到了反应物、过渡态、中间体和产物的几何构型,并计算了在蛋白质或水环境下有或没有肝醇脱氢酶时的反应势垒.结果表明,没有催化剂时,乙醇负离子的形成及其被氧化生成乙醛的反应势垒都很高,常温下反应难以进行;当肝醇脱氢酶存在时,乙醇负离子可以与肝醇脱氢酶中的Zn2+配位形成络合物,从而极大地降低了这两步的反应势垒,使得反应在常温下容易进行.

The mechanism of ethanol oxidation to aldehyde catalyzed by liver alcohol dehydrogenase in water and in protein environments was studied by the density function theory B3LYP method.The optimal structure of reactants,transition states,intermediates,and products were located at the B3LYP/6-31G^＊＊ level of theory.The reaction barriers were then calculated and compared in water and in protein at the B3LYP/6-311＋＋G（3df,2p） level of theory.The calculation results show that a high reaction barrier exists for the pathway where no catalyst is involved,suggesting that the oxidation cannot take place at room temperature without catalysts.A low reaction barrier exists when the liver alcohol dehydrogenase is involved,indicating that the liver alcohol dehydrogenase catalyzed reaction can take place at room temperature.The role of the liver alcohol dehydrogenase in the reaction was explored.