Zhao Xuerui, Zhang Hao, Shen Xiaoli, Zheng Qingchuan, Wang Song
Institute of Theoretical Chemistry, Jilin University, Changchun 130021, China.
School of Pharmaceutical Sciences, Jilin University, Changchun 130021, China.
Int J Mol Sci. 2025 Feb 26;26(5):2021. doi: 10.3390/ijms26052021.
Heptachlor (HEP) is an insecticide metabolized by cytochrome P450 (CYP) enzymes in the human liver, resulting in the formation of heptachlor epoxide (HEPX). HEPX can persist in the human body for a long duration. Therefore, it can be extremely harmful. A comprehensive understanding of HEP's metabolic fate may provide a theoretical basis for mitigating associated hazards. However, the specific human CYP isoforms that metabolize HEP, and their metabolic mechanisms, remain unclear. In this study, eight human CYP isoforms were used as catalytic enzymes to investigate the metabolic mechanism of HEP using molecular docking, molecular dynamics simulations, and quantum mechanical calculations. These results indicate that HEP primarily binds to CYP enzymes through hydrophobic interactions, and that the binding positions of HEP are determined by the composition and shape of the hydrophobic pockets near the active site. Based on the reaction distance, CYP2A6, CYP3A4, and CYP3A5 were the only three enzymes that could metabolize HEP. The epoxidation of HEP catalyzed by the doublet state of compound I was effectively concerted, and the rate-determining step was the electrophilic attack of the oxygen atom on HEP. The energy barriers of the rate-determining step vary significantly among different enzymes. A comparison of these energy barriers suggested that CYP3A5 is the most likely enzyme for HEP catalysis in humans.
七氯（HEP）是一种杀虫剂，在人体肝脏中由细胞色素P450（CYP）酶代谢，生成七氯环氧化物（HEPX）。HEPX可在人体内长期存留。因此，它可能极具危害性。全面了解HEP的代谢归宿可为减轻相关危害提供理论依据。然而，代谢HEP的具体人类CYP同工酶及其代谢机制仍不清楚。在本研究中，使用八种人类CYP同工酶作为催化酶，通过分子对接、分子动力学模拟和量子力学计算来研究HEP的代谢机制。这些结果表明，HEP主要通过疏水相互作用与CYP酶结合，且HEP的结合位置由活性位点附近疏水口袋的组成和形状决定。基于反应距离，CYP2A6、CYP3A4和CYP3A5是仅有的三种能够代谢HEP的酶。化合物I的双重态催化HEP的环氧化反应有效协同进行，且速率决定步骤是氧原子对HEP的亲电攻击。速率决定步骤的能垒在不同酶之间有显著差异。对这些能垒的比较表明，CYP3A5是人类中最有可能催化HEP的酶。
