P450-Mediated Dehydrogenation Mechanisms

P450 介导的脱氢机制

• 批准号: 7338664
• 负责人: Garold S Yost
• 金额: $ 28.16万
• 依托单位: UNIVERSITY OF UTAH
• 依托单位国家: 美国
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-01-01 至 2009-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7338664
• 关键词: Acetylcysteine; Active Sites; Alkylation; Apoproteins; Behavior; Binding; Biochemical; CYP2B6 gene; CYP2E1 gene; CYP2F3 gene; CYP3A4 gene; Capsaicin; Characteristics; Chemicals; Cleaved cell; Complementary DNA; Cyanogen Bromide; Cytochrome P450; Deuterium; Drug Interactions; Electron Transport; Environment; Enzymes; Escherichia coli; Exhibits; Glutathione; Goals; Health; Human; Injury; Kinetics; Label; MALDI-TOF Mass Spectrometry; Mediating; Methods; Molecular; Numbers; Pathway interactions; Peptide Fragments; Pharmaceutical Preparations; Predisposition; Process; Production; Property; Recombinants; Research; Research Personnel; Site; Skatole; Specificity; Structure; Tamoxifen; Time; Toxic effect; Xenobiotics; analog; base; dehydrogenation; drug metabolism; enzyme substrate; human SLC25A5 protein; inhibitor/antagonist; insight; liquid chromatography mass spectrometry; molecular modeling; mutant; preference; programs; toxicant; zafirlukast

Bioactivation of xenobiotics to toxic intermediates through cytochrome P450 oxygenation mechanisms is a well recognized process. However, the production of electrophilic intermediates by several P450 enzymes (e.g. 1A2, 2B6, 2E1, 2F1, 3A4, and 4B1), through dehydrogenation pathways has only recently been investigated, and the mechanisms that govern selective dehydrogenation rather than oxygenation are not established. Several of the dehydrogenated intermediates are so reactive that they inactivate the P450 enzymes, generally through alkylation of active site nucleophilic residues. Research concerning the catalytic behavior of these specific P450 enzymes and their propensity to dehydrogenate rather than oxygenate substrates is vitally needed. The hypothesis of this research is: the unique catalytic mechanism(s) offacilitated electron transport that determines dehydrogenation by certain P450 enzymes results in xenobiotic-mediated injury and altered drug metabolism in humans. The specific goals of this application are to determine the characteristics of the enzyme active-site environment that direct dehydrogenation mechanisms of specific cytochrome P450 enzymes, and to define the substrate structural features that regulate selective dehydrogenation rather than oxygenation. These goals will be realized through the following aims: 1) To determine the structures of the reactive intermediates that are produced by dehydrogenation of prototypical substrates, and characterize enzyme preferences for dehydrogenation vs. oxygenation of the substrates; 2) To characterize the mechanisms of inactivation of each P450 enzyme by its specific inactivator; 3) To define the active-site parameters that control the mechanisms of dehydrogenation and bioactivation of toxicants by P450 enzymes; and 4) To use the dehydrogenation substrates that covalently modify the P450 apoproteins to elucidate critical active-site residues that direct the dehydrogenation mechanism, or that control inhibitor/substrate access channels, binding, or product release. The enzyme/substrate pairs are CYP2F3/3-methylindole, CYP3A4/zafirlukast, CYP2El/capsaicin, and CYP2B6/tamoxifen. The long-term goals of this research are to elucidate the mechanisms of cytochrome P450-mediated dehydrogenation of xenobiotics in processes that generate toxic electrophilic intermediates, to assess the potential harm engendered by these toxic intermediates to human health, and to utilize mechanistic information to predict dehydrogenation, and concomitant toxicities and/or enzyme inactivation (altered drug metabolism), of new drugs and xenobiotics.

通过细胞色素P450氧化机制，外源药物对有毒中间体的生物活化是一个很好的途径