Structural Basis of Cytochrome P450 Activity

描述(申请人提供)：异种生物代谢细胞色素P450(P450)酶在药物代谢和毒素和致癌物前激活中起关键作用。由于每个P450都可以与多种底物和抑制剂相互作用，了解和预测外来化合物如何与这些酶结合并被这些酶代谢，在毒理学、化学预防和多药联用中具有重要的实用价值。基于现有的人类细胞色素P4502A酶和2E1酶的生物化学和结构生物学知识，本提案的目的是扩大、测试和应用我们对人2A酶和2E酶结构与其配体选择性之间的独特关系的理解。重要的是要了解每种酶的生理和药物代谢作用，以便操纵它们对人类健康产生积极影响。与这一提议相关的是，呼吸道中的2A13会激活烟草烟雾中最常见的两种致癌化合物之一，产生使DNA烷化的代谢物，并可能引发肺癌。选择性抑制2A13将显著减少这一过程。具体地说，我们建议1)用生理相关化合物和标记化合物来确定人细胞色素P450 2A和2E酶的结构，以扩大和测试我们对这些酶中配体结合的理解；2)建立并应用配基与人膜细胞色素P450酶结合的溶液核磁共振分析；以及3)鉴定和设计有效的、选择性的2A13抑制剂，以潜在地开发为肺癌化学预防药物。在这些研究完成后，我们希望能够确定2A酶的现有结构是否足以预测新药和小分子的结合，是否已经提出了减少烟草相关肺癌的抑制剂，并已经开发和验证了溶液核磁共振作为一种有价值的正交技术来研究配体结合。这些结果通过开发询问P450配体结合的新方法间接地推进了NIH的目标，并直接导致了一种减少人类肺癌的新的治疗方法。 与公共健康相关：这项提案调查了参与药物分解和人类致癌物质形成的酶。通过了解不同的药物和外来化学物质如何结合，然后被这些酶分解，我们可以更好地预测新药和已知致癌物是如何在人体内处理和消除的。这种知识的一个具体应用是开发一种药物，这种药物可以降低人体将尼古丁转化为DNA损伤分子的能力，这种分子可能会导致吸烟者患肺癌。

DESCRIPTION (provided by applicant): Xenobiotic-metabolizing cytochrome P450 (P450) enzymes play key roles in drug metabolism and toxin and procarcinogen activation. Since each P450 can interact with a wide range of substrates and inhibitors, understanding and predicting how foreign compounds bind and are metabolized by these enzymes is of great practical value in toxicology, chemoprevention, and polypharmacy. Building on existing knowledge in the biochemistry and structural biology of human cytochrome P450 2A and 2E1 enzymes, the objective of this proposal is to expand, test, and apply our understanding of the unique relationships between the structures of human 2A and 2E enzymes and their ligand selectivity. It is important to be able to understand the physiological and drug metabolism roles of each enzyme in order to manipulate them to positively affect human health. Relevant to this proposal, 2A13 in the respiratory track activates one of the two most prevalent and carcinogenic compounds in tobacco smoke to produce metabolites that alkylate DNA and can initiate lung cancer. Selective inhibition of 2A13 would significantly reduce this process. Specifically, we propose to 1) determine structures of human cytochrome P450 2A and 2E enzymes with physiologically relevant and marker compounds to both expand and test our understanding of ligand binding in these enzymes, 2) develop and apply a solution NMR assay of ligand binding to human membrane cytochrome P450 enzymes, and 3) identify and design potent, selective inhibitors of 2A13 for potential development as lung cancer chemopreventatives. At the completion of these studies, we expect to be able to determine if existing structures of 2A enzymes are sufficient to predict binding of new drugs and small molecules, to have proposed inhibitors to reduce tobacco- related lung cancer, and to have developed and validated solution NMR as a valuable orthogonal technique to investigate ligand binding. These results advance NIH goals indirectly by developing new methods to interrogate P450 ligand binding and directly by leading to a novel therapeutic approach for the reduction of human lung cancer. PUBLIC HEALTH RELEVANCE: This proposal investigates enzymes involved in the breakdown of drugs and the formation of carcinogens in humans. By understanding how different drugs and foreign chemicals bind and are then broken down by these enzymes, we can better predict how new drugs and known carcinogens are processed and eliminated in the human body. One specific application of this knowledge is the development of a drug that reduces the body's ability to convert nicotine into DNA-damaging molecules that can cause lung cancer in smokers.