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采用密度泛函(B3LYP)理论对乳清酸核苷单磷酸盐脱羧酶(ODCase)催化乳清酸核苷单磷酸盐(OMP)脱羧反应的动力学同位素效应进行了理论计算研究,重点讨论分析了水分子对整个催化脱羧反应的影响。本文建立了包含水分子和残基的新分子模型,并对所有分子模型进行结构全优化,获得了反应势垒。计算了N-1的~(15)N动力学同位素效应和C-6的~(13)C动力学同位素效应。计算结果显示:质子化水分子与羧基上的两个羰基氧原子的氢键长度对催化脱羧反应势垒有很大影响,并且计算得到的~(15)N和~(13)C动力学同位素效应与实验结果吻合较好。这些结果都对我们提出的乳清酸核苷单磷酸盐催化脱羧反应机理提供了有利依据。
The kinetic isotope effect of the orotidine monophosphate decarboxylase (ODCase) on the decarboxylation of orotidine monophosphate (OMP) catalyzed by density functional theory (B3LYP) has been studied theoretically. The effect of water molecules on the entire catalytic decarboxylation. In this paper, a new molecular model containing water molecules and residues has been established, and all the molecular models have been optimized in structure, and the reaction barrier has been obtained. The ~ (15) N kinetic isotope effect of N-1 and the ~ (13) C kinetic isotope effect of C-6 were calculated. The calculated results show that the hydrogen bond lengths between protonated water molecules and two carbonyl oxygen atoms on the carboxyl group greatly influence the catalytic decarboxylation reaction barrier, and the calculated ~ (15) N and ~ (13) C kinetic isotopes The effect is in good agreement with the experimental results. These results provide a good basis for our proposed catalytic decarboxylation mechanism of orotidine monophosphate.