Yamazaki H, Inoue K, Shaw P M, Checovich W J, Guengerich F P, Shimada T
Osaka Prefectural Institute of Public Health, 3-69 Nakamichi 1-chome, Higashinari-ku, Osaka 537, Japan.
J Pharmacol Exp Ther. 1997 Nov;283(2):434-42.
Omeprazole 5-hydroxylation and sulfoxidation activities were determined in liver microsomes of different humans whose levels of individual forms of cytochrome P450 (P450 or CYP) varied. Correlation coefficients between omeprazole 5-hydroxylation activities (when determined at a substrate concentration of 10 microM) and S-mephenytoin 4'-hydroxylation and testosterone 6beta-hydroxylation activities were found to be 0.64 and 0.67, respectively, in liver microsomes of 84 human samples examined. Omeprazole sulfoxidation activities in these human samples were correlated with testosterone 6beta-hydroxylation activities (r = 0. 86). Omeprazole 5-hydroxylation by liver microsomes of a human sample that contained relatively high levels of CYP3A4 and low levels of CYP2C19 were inhibited very significantly by ketoconazole and anti-CYP3A4 antibodies, although a human sample having high in CYP2C19 and low in CYP3A4 was found to be sensitive toward fluvoxamine and anti-CYP2C9 antibodies. Sulfaphenazole (at 100 microM) did not affect the omeprazole 5-hydroxylation and sulfoxidation catalyzed by human liver microsomes. Both recombinant human CYP2C19 and CYP3A4 enzymes had activities for omeprazole 5-hydroxylation, with low Km and high Vmax values for the former enzyme and high Km and low Vmax values for the CYP3A4. These results suggest that contributions of CYP2C19 and CYP3A4 in the omeprazole 5-hydroxylation depend upon the ratio of these two P450 levels in human liver microsomes. Omeprazole 5-hydroxylation activities of different human samples were found to be related to predicted values calculated from the kinetic parameters of recombinant enzymes and the levels of liver microsomal CYP2C19 and CYP3A4 enzymes. Finally, when recombinant human CYP2C19 and CYP3A4 were mixed at levels found in different human samples, relatively similar profiles of omeprazole oxidation by the recombinant and microsomal enzyme systems were determined by analysis of high-performance liquid chromatography. These results suggest that both CYP2C19 and CYP3A4 are involved in the 5-oxidation of omeprazole (at a substrate concentration of 10 microM) in human liver microsomes and that contributions of these P450 enzymes depend on the compositions of CYP2C19 and CYP3A4 in liver.
在细胞色素P450（P450或CYP）各亚型水平不同的不同个体的肝脏微粒体中，测定了奥美拉唑5-羟化和亚砜化活性。在所检测的84份人类样本的肝脏微粒体中，发现奥美拉唑5-羟化活性（在底物浓度为10μM时测定）与S-美芬妥因4'-羟化和睾酮6β-羟化活性之间的相关系数分别为0.64和0.67。这些人类样本中的奥美拉唑亚砜化活性与睾酮6β-羟化活性相关（r = 0.86）。酮康唑和抗CYP3A4抗体对含有相对高水平CYP3A4和低水平CYP2C19的人类样本的肝脏微粒体催化的奥美拉唑5-羟化有非常显著的抑制作用，尽管发现CYP2C19含量高而CYP3A4含量低的人类样本对氟伏沙明和抗CYP2C9抗体敏感。磺胺苯吡唑（100μM）不影响人肝脏微粒体催化的奥美拉唑5-羟化和亚砜化。重组人CYP2C19和CYP3A4酶均具有奥美拉唑5-羟化活性，前者酶的Km值低、Vmax值高，而CYP3A4的Km值高、Vmax值低。这些结果表明，CYP2C19和CYP3A4在奥美拉唑5-羟化中的作用取决于人肝脏微粒体中这两种P450水平的比例。发现不同人类样本的奥美拉唑5-羟化活性与根据重组酶的动力学参数以及肝脏微粒体CYP2C19和CYP3A4酶水平计算出的预测值相关。最后，当将重组人CYP2C19和CYP3A4按不同人类样本中发现的水平混合时，通过高效液相色谱分析确定了重组酶和微粒体酶系统对奥美拉唑氧化的相对相似的图谱。这些结果表明，CYP2C19和CYP3A4均参与人肝脏微粒体中奥美拉唑（在底物浓度为10μM时）的5-氧化，并且这些P450酶的作用取决于肝脏中CYP2C19和CYP3A4的组成。
