Strobl G R, von Kruedener S, Stöckigt J, Guengerich F P, Wolff T
Institut für Toxikologie, GSF-Forschungszentrum für Umwelt und Gesundheit, Neuherberg, Germany.
J Med Chem. 1993 Apr 30;36(9):1136-45. doi: 10.1021/jm00061a004.
To gain insight into the specificity of cytochrome P-450 2D6 toward inhibitors, a preliminary pharmacophore model was built up using strong competitive inhibitors. Ajmalicine (1), the strongest inhibitor known (Ki = 3 nM) was selected as template because of its rigid structure. The preliminary pharmacophore model was validated by performing inhibition studies with derivatives of ajmalicine (1) and quinidine (9). Bufuralol (18) was chosen as substrate and the metabolite 1'-hydroxybufuralol (19) was separated by high performance liquid chromatography. All incubations were carried out using human liver microsomes after demonstration that the Ki values obtained with microsomes were in accordance with those obtained with a reconstituted monooxygenase system containing purified cytochrome P-450 2D6. Large differences of Ki values ranging between 0.005 and 100 microM were observed. Low-energy conformers of tested compounds were fit within the preliminary pharmacophore model. The analysis of steric and electronic properties of these compounds led to the definition of a final pharmacophore model. Characteristic properties are a positive charge on a nitrogen atom and a flat hydrophobic region, the plane of which is almost perpendicular to the N-H axis and maximally extends up to a distance of 7.5 A from the nitrogen atom. Compounds with high inhibitory potency had additional functional groups with negative molecular electrostatic potential and hydrogen bond acceptor properties on the opposite side at respective distances of 4.8-5.5 A and 6.6-7.5 A from the nitrogen atom. The superposition of strong and weak inhibitors led to the definition of an excluded volume map. Compounds that required additional space were not inhibitors. This is apparently the first pharmacophore model for inhibitors of a cytochrome P-450 enzyme and offers the opportunity to classify compounds according to their potency of inhibition. Adverse drug interactions which occur when both substrates and inhibitors of cytochrome P-450 2D6 are applied may be predicted.
为深入了解细胞色素P - 450 2D6对抑制剂的特异性，使用强效竞争性抑制剂建立了初步的药效团模型。由于阿吗灵（1）结构刚性，它是已知最强的抑制剂（Ki = 3 nM），因此被选作模板。通过对阿吗灵（1）和奎尼丁（9）的衍生物进行抑制研究，对初步药效团模型进行了验证。选择布非洛尔（18）作为底物，其代谢产物1'-羟基布非洛尔（19）通过高效液相色谱法分离。在用微粒体获得的Ki值与用含有纯化细胞色素P - 450 2D6的重组单加氧酶系统获得的Ki值一致后，所有孵育均使用人肝微粒体进行。观察到Ki值在0.005至100 microM之间存在很大差异。将测试化合物的低能量构象拟合到初步药效团模型中。对这些化合物的空间和电子性质分析得出了最终的药效团模型。其特征性质是氮原子上的正电荷和一个平面疏水区域，该平面几乎垂直于N - H轴，且从氮原子最大延伸至7.5 Å的距离。具有高抑制效力的化合物在相对侧分别距氮原子4.8 - 5.5 Å和6.6 - 7.5 Å处具有带有负分子静电势和氢键受体性质的额外官能团。强效和弱效抑制剂的叠加导致了排除体积图的定义。需要额外空间的化合物不是抑制剂。这显然是细胞色素P - 450酶抑制剂的首个药效团模型，为根据化合物的抑制效力对其进行分类提供了机会。当同时应用细胞色素P - 450 2D6的底物和抑制剂时可能发生的药物不良相互作用也可得到预测。
