Abstract: 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.

Key words: liver alcohol dehydrogenase, ethanol anion, density functional theory, reaction mechanism, zinc ion, acetaldehyde