Five distinct human cytochromes mediate amitriptyline N-demethylation in vitro: dominance of CYP 2C19 and 3A4.
Five distinct human cytochromes mediate amitriptyline N-demethylation in vitro: dominance of CYP 2C19 and 3A4.
复制标题
五种不同的人类细胞色素在体外介导阿米替林 N-去甲基化：CYP 2C19 和 3A4 占主导地位。
DOI：
10.1002/j.1552-4604.1998.tb04399.x
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发表时间：
1998
影响因子：
2.9
通讯作者：
Shader,RI
中科院分区：
文献类型：
--
作者：
Venkatakrishnan,K;Greenblatt,DJ;vonMoltke,LL;Schmider,J;Harmatz,JS;Shader,RI
人类细胞色素P450 （CYPs）介导阿米替林N -去甲基化已经通过酶动力学和化学抑制研究的组合被确定。用cDNA转染的表达人CYPs 1A2、2C9、2C19、2D6和3A4的人淋巴母细胞微粒体将阿米替林N‐去甲基化为去甲替林。CYP 2E1无明显活性。CYP 2C19和CYP 2D6具有高亲和力，CYP 3A4具有低亲和力；CYP 2C9与1A2具有中等亲和力。基于这些动力学参数和估计的人类肝脏中不同CYPs的相对丰度，CYP 2C19被确定为低（治疗相关）阿米替林浓度下主要的阿米替林N‐去甲基化酶，而CYP 3A4可能在高阿米替林浓度下更重要。酮康唑和奥美拉唑的化学抑制研究表明，在阿米替林浓度为100 μmol/L时，CYP 3A4是主要的阿米替林N‐去甲基化酶，而在底物浓度为5 μmol/L时，CYP 2C19同样重要。在两种底物浓度下，CYP 1A2抑制剂α -萘黄酮和CYP 2C9抑制剂磺胺苯唑对阿米替林N -去甲基化的抑制作用都要小得多。奎尼丁无明显抑制作用。人肝微粒体对阿米替林N‐去甲基化的动力学符合双酶模型，高亲和组分表现为Michaelis Menten动力学，低亲和组分表现为Hill酶动力学。在两个具有低水平CYP 2C19活性的肝脏样本中，阿米替林N‐去甲基化动力学与另外两个具有相对正常2C19活性的肝脏样本相比没有明显差异。这可能反映了较高的底物浓度值在体外动力学参数估计中的重要性。
The human cytochromes P450 (CYPs) mediating amitriptyline N‐demethylation have been identified using a combination of enzyme kinetic and chemical inhibition studies. Amitriptyline was N‐demethylated to nortriptyline by microsomes from cDNA transfected human lymphoblastoid cells expressing human CYPs 1A2, 2C9, 2C19, 2D6, and 3A4. CYP 2E1 showed no detectable activity. While CYP 2C19 and CYP 2D6 showed high affinity, CYP 3A4 showed low affinity; CYP 2C9 and 1A2 showed intermediate affinities. Based on these kinetic parameters and estimated relative abundance of the different CYPs in human liver, CYP 2C19 was identified as the major amitriptyline N‐demethylase at low (therapeutically relevant) amitriptyline concentrations, whereas CYP 3A4 may be more important at higher amitriptyline concentrations. Chemical inhibition studies with ketoconazole and omeprazole indicate that CYP 3A4 is the major amitriptyline N‐demethylase at 100 μmol/L amitriptyline, while CYP 2C19 is equally important at a substrate concentration of 5 μmol/L. The CYP 1A2 inhibitor α‐naphthoflavone and the CYP 2C9 inhibitor sulfaphenazole produced much less inhibition of amitriptyline N‐demethylation at both substrate concentrations. Quinidine produced no detectable inhibition. The kinetics of amitriptyline N‐demethylation by human liver microsomes were consistent with a two enzyme model, with the high affinity component exhibiting Michaelis Menten kinetics and the low affinity component exhibiting Hill enzyme kinetics. No difference was apparent in the kinetics of amitriptyline N‐demethylation in two liver samples with low levels of CYP 2C19 activity compared with two other samples with relatively normal 2C19 activity. This may reflect the importance of higher substrate concentration values in estimation of kinetic parametersin vitro.