Catalytic mechanism of cytochrome P450 for N-methylhydroxylation of nicotine: reaction pathways and regioselectivity of the enzymatic nicotine oxidation.
Catalytic mechanism of cytochrome P450 for N-methylhydroxylation of nicotine: reaction pathways and regioselectivity of the enzymatic nicotine oxidation.
复制标题
DOI：
10.1039/c2dt32106h
复制
发表时间：
2013-03-21
期刊：
影响因子：
--
通讯作者：
Zhan CG
中科院分区：
文献类型：
--
作者：
Li D;Huang X;Lin J;Zhan CG
通过赝键第一性原理量子力学/分子力学（QM/MM）反应坐标计算，研究了细胞色素P450 2A6 （CYP2A6）催化(S)-(−)-尼古丁n-甲基羟化反应的基本机理和自由能谱。在CYP2A6-(S)-(−)-尼古丁结合结构中，允许5 ' -羟基化，n -甲基也足够靠近Cpd I的氧，以发生n -甲基羟基化反应。研究表明，cyp2a6催化的n-甲基羟化反应是一个协调的过程，涉及氢转移过渡态在四重态和双重态上。n -甲基羟化反应主要在重态上进行，因为重态上的自由能垒比四重态上的自由能垒要低。计算得到的自由能势垒表明，CYP2A6催化的(S)-(−)-烟碱氧化过程对5′位置的氢进行了高区域选择性的提取，而不是n -甲基上的氢。预测的区域选择性为93%，与最近实验报道的95%的区域选择性一致。(S)-(−)-尼古丁在CYP2A6活性位点的结合方式是尼古丁(S)-(−)-氧化的立体选择性的重要决定因素，而(S)-(−)-尼古丁氧化的区域选择性主要由5′-羟基化反应和n -甲基羟基化反应之间的自由能垒差决定。
The fundamental reaction mechanism of cytochrome P450 2A6 (CYP2A6)-catalyzed N-methylhydroxylation of (S)-(−)-nicotine and the free energy profile have been studied by performing pseudobond first-principles quantum mechanical/molecular mechanical (QM/MM) reaction-coordinate calculations. In the CYP2A6-(S)-(−)-nicotine binding structures that allow for 5′-hydroxylation, the N-methyl group is also sufficiently close to the oxygen of Cpd I for the N-methylhydroxylation reaction to occur. It has been demonstrated that the CYP2A6-catalyzed N-methylhydroxylation reaction is a concerted process involving a hydrogen-transfer transition state on both the quartet and the doublet states. The N-methylhydroxylation reaction proceeds mainly on the doublet state, since the free energy barriers on the doublet state are lower than the corresponding ones on the quartet state. The calculated free energy barriers indicate that (S)-(−)-nicotine oxidation catalyzed by CYP2A6 proceeds with a high regioselective abstraction of the hydrogen at the 5′-position, rather than the hydrogen at the N-methyl group. The predicted regioselectivity of 93% is in agreement with the most recent experimental reported regioselectivity of 95%. The binding mode of (S)-(−)-nicotine in the active site of CYP2A6 is an important determinant for the stereoselectivity of nicotine (S)-(−)-oxidation, whereas the regioselectivity of (S)-(−)-nicotine oxidation is determined mainly by the free energy barrier difference between the 5′-hydroxylation and N-methylhydroxylation reactions.
登录
查看更多内容
影响因子：
5.5
作者：
Liu, Junjun;Zhan, Chang-Guo
通讯作者：
Zhan, Chang-Guo
影响因子：
15
作者：
JONES, JP;TRAGER, WF;CARLSON, TJ
通讯作者：
CARLSON, TJ
DOI：
10.1073/pnas.220207697
发表时间：
2000-11-07
影响因子：
11.1
作者：
Hecht, SS;Hochalter, JB;Murphy, SE
通讯作者：
Murphy, SE
DOI：
10.1007/bf03189632
发表时间：
1982-01-01
影响因子：
1.9
作者：
GORROD, JW;HIBBERD, AR
通讯作者：
HIBBERD, AR
影响因子：
4.1
作者：
CASHMAN, JR;PARK, SB;BENOWITZ, NL
通讯作者：
BENOWITZ, NL