鉴定CYP3A4和CYP2C8为人类肝微粒体中负责吗啡N-去甲基化的主要细胞色素P450酶。

Identification of CYP3A4 and CYP2C8 as the major cytochrome P450 s responsible for morphine N-demethylation in human liver microsomes.

Projean D, Morin P-E, Tu T M, Ducharme J

Faculté de Pharmacie, Université de Montréal, Montréal, Québec, Canada.

Xenobiotica. 2003 Aug;33(8):841-54. doi: 10.1080/0049825031000121608.

Abstract

The aim was to identify the cytochrome P450 (CYP) enzymes responsible for the N-demethylation of morphine in vitro. 2. In human liver microsomes, normorphine formation followed Michaelis-Menten kinetics with mean Km and Vmax of 12.4 +/- 2.2 mM and 1546 +/- 121 pmol min(-1) mg(-1), respectively. In microsomes from a panel of 14 human livers phenotyped for 10 CYP enzymes, morphine N-demethylation correlated with testosterone 6beta-hydroxylation (r=0.91, p<0.001) and paclitaxel 6-alpha hydroxylation (r=0.72, p<0.001), two specific markers of CYP3A4 and CYP2C8, respectively. Normorphine formation decreased when incubated in the presence of troleandomycin or quercetin (by 46 and 33-36%, respectively), which further corroborates the contribution of CYP3A4 and CYP2C8. 3. Among eight recombinant human CYP enzymes tested, CYP3A4 and CYP2C8 exhibited the highest intrinsic clearance. More than 90% of morphine N-demethylation could be accounted for via the action of both CYP3A4 and CYP2C8. 4. The in vitro findings suggest that hepatic CYP3A4, and to a lesser extent CYP2C8, play an important role in the metabolism of morphine into normorphine.

摘要

目的是在体外鉴定负责吗啡N-去甲基化的细胞色素P450（CYP）酶。2. 在人肝微粒体中，去甲吗啡的形成遵循米氏动力学，平均Km和Vmax分别为12.4±2.2 mM和1546±121 pmol min⁻¹ mg⁻¹。在对10种CYP酶进行表型分析的14个人肝脏的微粒体中，吗啡N-去甲基化与睾酮6β-羟基化（r = 0.91，p <0.001）和紫杉醇6-α羟基化（r = 0.72，p <0.001）相关，这两个分别是CYP3A4和CYP2C8的特异性标志物。在存在三乙酰竹桃霉素或槲皮素的情况下孵育时，去甲吗啡的形成减少（分别减少46%和33 - 36%），这进一步证实了CYP3A4和CYP2C8的作用。3. 在测试的8种重组人CYP酶中，CYP3A4和CYP2C8表现出最高的内在清除率。超过90%的吗啡N-去甲基化可通过CYP3A4和CYP2C8的共同作用来解释。4. 体外研究结果表明，肝脏中的CYP3A4以及程度较轻的CYP2C8在将吗啡代谢为去甲吗啡的过程中起重要作用。