Cytochrome P-450 Polymorphism

描述(申请人提供)：本申请的目的是确定确定人类微粒体细胞色素P450酶底物特异性的结构特征。这些蛋白质参与结构多样的药物、环境毒素和致癌物的新陈代谢，并提供对化学侮辱的广泛防御。虽然这些酶可以代谢多种化合物，但它们表现出不同的底物特征。等位基因变异可以选择性地改变代谢能力，限制主要由单个P450代谢的化合物的安全暴露。同源酶之间的物种差异表明，对人类P450酶的彻底表征将为预测药物代谢和化学暴露的风险提供最可靠的手段。兔2C5的结构特征提供了关于活性部位结构和底物结合时发生的构象变化的见解。人类2C酶包括2C9的四个等位变异，将通过X射线衍射研究进行表征。活性部位的体积和拓扑结构对底物选择性、区域和立体专一性、竞争抑制、催化能力和激活催化的药物-药物相互作用的影响将通过对已知底物和抑制剂的定点突变和类似物面板进行检测。将分析高度保守的天冬氨酸残基所起的作用。还将评估P450构象灵活性的程度和底物相关性，以确定支配底物识别的动态活性部位特征。这些分析将扩展到各种家族2 P450酶，以开发更全面和一致的P450催化图像。这些信息将为合理的药物设计和风险评估提供实践依据。

DESCRIPTION (provided by applicant): The objective of this application is to define the structural features that determine the substrate specificities of human microsomal cytochrome P450 enzymes. These proteins participate in the metabolism of structurally diverse drugs, environmental toxins and carcinogens, and provide a broad defense against chemical insults. Although these enzymes can metabolize a wide range of compounds, they exhibit distinct substrate profiles. Allelic variation can selectively alter metabolic capacity and limit safe exposure to compounds that are predominantly metabolized by a single P450. Species differences between orthologous enzymes indicate that thorough characterization of the human P450 enzymes will provide the most reliable means for predicting drug metabolism and the risks of chemical exposure. Structural characterization of rabbit 2C5 has provided insights regarding active site architecture and conformational changes that occur with substrate binding. The human 2C enzymes including four allelic variants of 2C9 will be characterized by x-ray diffraction studies. The influence of active site volume and topology on substrate selectivity, regio and stereo-specificity, competitive inhibition, catalytic competence, and drug-drug interactions that activate catalysis will be examined using site directed mutagenesis and panels of analogs for known substrates and inhibitors. The role played by a highly conserved aspartate residue will be analyzed. The extent and substrate dependence of P450 conformational flexibility will also be evaluated to determine dynamic active site characteristics that govern substrate recognition. These analyses will be extended to various family 2 P450 enzymes in order to develop a more comprehensive and coherent picture of P450 catalysis. This information will provide a practical basis for rational drug design and risk assessment.