牛磺酸/ $α$ -酮戊二酸双加氧酶羟基化过程中的原子隧道效应的量子力学/分子力学模拟
Atom Tunneling in the Hydroxylation Process of Taurine/$α$-Ketoglutarate Dioxygenase Identified by Quantum Mechanics/Molecular Mechanics Simulations
摘要：
TauD双加氧酶是研究最多的$α$ -酮戊二酸依赖性双加氧酶（$α$ KGD）之一，涉及多种生物技术应用。我们采用量子力学/MM方法（B3 LYP/CHARMM 22）研究了$α$ KGD催化循环中的关键步骤--氢转移过程。在反应过程中的电荷和自旋密度的分析表明，一个协调的机制发生，其中的H原子转移发生的同时，从牛磺酸的Fe=O辅因子的电子转移。我们发现氢原子的量子隧穿使速率常数在5 \textcelsius{}时增加40倍。因此，获得了接近60的相当高的KIE值，这与实验值一致。
英文摘要：
TauD dioxygenase is one of the most studied $α$-ketoglutarate dependent dioxygenases ($α$KGDs), involved in several biotechnological applications. We investigated the key step in the catalytic cycle of the $α$KGDs, the hydrogen transfer process, by a QM/MM approach (B3LYP/CHARMM22). Analysis of the charge and spin densities during the reaction demonstrates that a concerted mechanism takes place, where the H atom transfer happens simultaneously with the electron transfer from taurine to the Fe=O cofactor. We found quantum tunneling of the hydrogen atom to increase the rate constant by a factor of 40 at 5\textcelsius{}. As a consequence a quite high KIE value of close to 60 is obtained, which is consistent with the experimental value.
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