Cytochrome P-450 Polymorphism

描述(申请人提供)：肝脏、微粒体、细胞色素P450单加氧酶在新陈代谢和清除多种药物、毒素和内生菌方面具有重要的保护作用。这项应用的长期目标是确定决定单个人P450酶底物选择性的结构特征。活性中心特征影响底物选择性、抑制电位、药物氧化的区域选择性，以及药物-药物相互作用和激活动力学的发生。比较P450 1A2、2A6、2C8、2C9和3A4与底物或抑制剂的复合体的最新结构，表明每个活性中心对底物选择性的独特方面，包括水化状态、活性中心残基的化学特征和定位，以及活性中心拓扑结构的变化对这些结合决定因素的影响。这强调了有必要确定结构不同的药物复合体中单个酶的多种结构，以了解构象灵活性对药物结合的贡献。将确定P450的1A2、2D6、2C19和2C9*3活性部位结构的特定变化，这些变化是由单独或联合使用化学上不同的底物、抑制剂和激活剂引起的，以描述每种酶可能发生的适应性变化的范围。P450 2A6是人体内主要的尼古丁氧化酶。对含有不同抑制剂的复合体中2A6活性部位的分析表明，有几个相对静态的特征可以有效地用于基于结构的设计，更有效和选择性的抑制剂将具有潜在的戒烟辅助作用。将评估先导化合物与活性部位的互补性、结合强度以及2A6相对于其他P450的特异性。还将确定P450酶1B1、3A5和3A7的活性部位拓扑，以确定控制这些酶对药物代谢的重要功能贡献的结构特征。总而言之，这些研究将解决我们对P450结构与功能相关的知识的重大空白，并为预测药物代谢提供重要的信息和工具。

DESCRIPTION (provided by applicant): Hepatic, microsomal, cytochrome P450 monooxygenases provide a crucial protective role in the metabolism and clearance of a wide array of drugs, toxins and endobiotics. The long term objective of this application is to identify structural features that determine the substrate selectivity of individual human P450 enzymes. Active site characteristics affect substrate selectivity, inhibitory potential, the regioselectivity of drug oxidation, as well as the occurrence of drug-drug interactions and activation kinetics. Comparison of recent structures for P450s 1A2, 2A6, 2C8, 2C9 and 3A4 in complex with substrates or inhibitors indicate unique aspects of each active site that contribute to substrate selectivity including the hydration state, the chemical characteristics and positioning of active site residues, as well as the changes imposed on these binding determinants by alterations in active site topology. This underscores the necessity to determine multiple structures of individual enzymes in complex with structurally dissimilar drugs to understand the contribution of conformational flexibility to drug binding. Specific changes in the active site architectures of P450s 1A2, 2D6, 2C19 and 2C9*3 induced by interaction with chemically diverse substrates, inhibitors and activators, alone or in combination, will be identified to delineate the range of adaptive changes that can occur for each enzyme. P450 2A6 is the principal nicotine oxidase in humans. Analysis of the 2A6 active site in complex with different inhibitors indicates several relatively static features that can be productively exploited for the structure based design of more efficacious and selective inhibitors that would have potential benefits as therapeutic aids for smoking cessation. Lead compounds will be assessed for complementarity with the active site, strength of binding, and specificity for 2A6 relative to other P450s. The active site topologies of P450s 1B1, 3A5 and 3A7 will also be determined to identify structural characteristics that control the important functional contribution made by these enzymes to drug metabolism. Collectively, these studies will address significant gaps in our knowledge of P450 structure as it relates to function, and provide important information and tools for prediction of drug metabolism.