Cytochrome P450 isoforms involved in metabolism of the enantiomers of verapamil and norverapamil
Cytochrome P450 isoforms involved in metabolism of the enantiomers of verapamil and norverapamil
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DOI：
10.1046/j.1365-2125.1999.00923.x
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发表时间：
1999-05-01
影响因子：
3.4
通讯作者：
Wainer, IW
中科院分区：
文献类型：
--
作者：
Tracy, TS;Korzekwa, KR;Wainer, IW
目的本研究进行评估代谢的维拉帕米和norverapamil对映体使用广泛的细胞色素P450亚型和测量动力学参数的这些processes.Methods细胞色素P450 cDNA表达细胞和微粒体从P450表达淋巴母细胞系孵育浓度为40 μ M的R-或S-维拉帕米和R-或S-通过h.p.l.c.测量去甲维拉帕米和代谢物形成。作为初步筛选。这些异构体表现出实质性的活动，然后研究了在一个范围内的底物浓度（2.5-450 μ M），以估计代谢产物formation.Results的动力学参数P450的3A 4，3A 5，2C 8和在较小程度上2 E1参与代谢的维拉帕米的对映体。P450 3A 4和3A 5产生D-617和去甲维拉帕米的估计Km值相似（范围= 60-127 μ M），与研究的维拉帕米对映体无关，而V-max估计值也相似（范围= 4-8 pmol min（-1）pmol（-1）P450）。仅观察到这些亚型的D-620标称产量。有趣的是，P450 2C 8容易将S-和R-维拉帕米代谢为D-617、去甲维拉帕米和PR-22，K-m值仅略高于P450 3A 4和3A 5。然而，S-和R-维拉帕米的P450 2C 8代谢的Vmax估计值通常大于（范围= 8-15 pmol min（-1）pmol（-1）P450）P450 s 3A 4和3A 5的Vmax估计值，S-对映体的代谢更受欢迎。同样，P450的3A 4，3A 5和2C 8也介导的代谢的对映体的norverapamil与较小的贡献P450的2D 6和2 E1。P450 3A 4和3A 5容易形成D-620代谢物，S-去甲维拉帕米的Km和Vmax通常低于R-对映体。与此相反，P450 2C 8产生的D-620和PR-22代谢物的对映体的norverapamil，再次与立体选择性偏好看到的S-对映体。结论这些结果证实，P450的3A 4，3A 5和2C 8发挥了重要作用，维拉帕米的代谢，并证明norverapamil也可以进一步代谢的P450。
Aims The present study was conducted to evaluate metabolism of the enantiomers of verapamil and norverapamil using a broad range of cytochrome P450 isoforms and measure the kinetic parameters of these processes.Methods Cytochrome P450 cDNA-expressed cells and microsomes from a P450-expressed lymphoblastoid cell line were incubated with 40 mu M concentrations of R- or S-verapamil and R- or S-norverapamil and metabolite formation measured by h.p.l.c. as an initial screening. Those isoforms exhibiting substantial activity were then studied over a range of substrate concentrations (2.5-450 mu M) to estimate the kinetic parameters for metabolite formation.Results P450s 3A4, 3A5, 2C8 and to a minor extent 2E1 were involved in the metabolism of the enantiomers of verapamil. Estimated K-m values for the production of D-617 and norverapamil by P450s 3A4 and 3A5 were similar (range = 60-127 mu M) regardless of the enantiomer of verapamil studied while the V-max estimates were also similar (range = 4-8 pmol min(-1) pmol(-1) P450). Only nominal production of D-620 by these isoforms was noted. Interestingly, P450 2C8 readily metabolized both S- and R-verapamil to D-617, norverapamil and PR-22 with only slightly higher K-m values than noted for P450s 3A4 and 3A5. However, the V-max estimates for P450 2C8 metabolism of S- and R-verapamil were in general greater (range = 8-15 pmol min(-1) pmol(-1) P450) than those noted for P450 s 3A4 and 3A5 with preference noted for metabolism of the S-enantiomer. Similarly, P450 s 3A4, 3A5 and 2C8 also mediated the metabolism of the enantiomers of norverapamil with minor contributions by P450 s 2D6 and 2E1. P450s 3A4 and 3A5 readily formed the D-620 metabolite with generally a lower K-m and higher V-max for S-norverapamil than for the R-enantiomer. In contrast, P450 2C8 produced both the D-620 and PR-22 metabolites from the enantiomers of norverapamil, again with stereoselective preference seen for the S-enantiomer.Conclusions These results confirm that P450s 3A4, 3A5 and 2C8 play a major role in verapamil metabolism and demonstrate that norverapamil can also be further metabolized by the P450s.