Zhou Y-H, Zheng Q-C, Li Z-S, Zhang Y, Sun M, Sun C-C, Si D, Cai L, Guo Y, Zhou H
State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023, China.
Biochimie. 2006 Oct;88(10):1457-65. doi: 10.1016/j.biochi.2006.05.001. Epub 2006 May 26.
Cytochrome P450 2C9 (CYP2C9) plays a key role in the metabolism of clinical drugs. CYP2C9 is a genetically polymorphic enzyme and some of its allelic variants have less activity compared to the wild-type form. Drugs with a narrow therapeutic index may cause serious toxicity to the individuals who carry such allele. CYP2C913, firstly identified by some of the present authors in a Chinese poor metabolizer of lornoxicam, is characterized by mutation encoding Leu90Pro substitution. Kinetic experiments show that CYP2C913 has less catalytic activity in elimination of diclofenac and lornoxicam in vitro. In order to explore the structure-activity relationship of CYP2C913, the three-dimensional structure models of the substrate-free CYP2C91 and its variant CYP2C913 are constructed on the basis of the X-ray crystal structure of human CYP2C91 (PDB code 1R9O) by molecular dynamics simulations. The structure change caused by Leu90Pro replacement is revealed and used to explain the dramatic decrease of the enzymatic activity in clearance of the two CYP2C9 substrates: diclofenac and lornoxicam. The trans configuration of the bond between Pro90 and Asp89 in CYP2C913 is firstly identified. The backbone of residues 106-108 in CYP2C913 turns over and their side chains block the entrance for substrates accessing so that the entrance of *13 shrinks greatly than that in the wild-type, which is believed to be the dominant mechanism of the catalytic activity reduction. Consequent docking study which is consistent with the results of the kinetic experiments by Guo et al. identifies the most important residues for enzyme-substrate complexes.
细胞色素P450 2C9（CYP2C9）在临床药物代谢中起关键作用。CYP2C9是一种具有遗传多态性的酶，其一些等位基因变体与野生型相比活性较低。治疗指数窄的药物可能会对携带此类等位基因的个体造成严重毒性。CYP2C913首先由本文部分作者在一名中国氯诺昔康慢代谢者中鉴定出来，其特征是编码Leu90Pro替代的突变。动力学实验表明，CYP2C913在体外消除双氯芬酸和氯诺昔康方面具有较低的催化活性。为了探索CYP2C913的构效关系，基于人CYP2C91的X射线晶体结构（PDB代码1R9O），通过分子动力学模拟构建了无底物CYP2C91及其变体CYP2C913的三维结构模型。揭示了Leu90Pro替代引起的结构变化，并用于解释两种CYP2C9底物双氯芬酸和氯诺昔康清除过程中酶活性的显著降低。首次鉴定了CYP2C913中Pro90和Asp89之间键的反式构象。CYP2C913中106 - 108位残基的主链翻转，其侧链阻碍底物进入的通道，因此*13的通道比野生型大大缩小，这被认为是催化活性降低的主要机制。随后与Guo等人的动力学实验结果一致的对接研究确定了酶 - 底物复合物中最重要的残基。
