BIOACTIVATION OF DIETARY PHENOLS BY HEMOPROTEINS

对天然存在的酚有很大的兴趣，因为 它们作为抗氧化剂和癌症治疗剂的巨大潜力 预防 不幸的是，这些物质也会导致 形成自由 自由基、突变、肿瘤和细胞毒性。 酚类物质的各种生物学效应的机制必须是 在这些因素之前阐明了影响有益的混合物 和行列式性质可以得到更充分的理解。 代谢 细胞色素P450对这些化合物的活化涉及公知的 活性代谢物，如环氧化物和醌，但苯氧基自由基 P450催化的单电子氧化反应产生的分子量 羟基对位的氧形成氢过氧-环己二烯酮， 在化学文献中称为“过氧喹啉”。这本小说 途径尚未得到广泛认可，因为过氧喹啉不 在生物系统中会迅速降解。 期间 在当前的资助期间，它已经被证明，使用一系列 烷基取代的酚，过氧醌醇的形成发生在 在肝微粒体和分离的肝细胞中均存在显著程度。 该途径的相对贡献受底物的影响 结构和P450同工酶。 过氧喹啉类化合物可被下列物质迅速降解： 各种血红素蛋白沿着复杂的途径，形成自由基， 亲电产物，选择性氧化完整的蛋氨酸残基 蛋白质，并严重损害细胞。 数据继续有力支撑 过氧喹啉类化合物在介导生物活性中作用的研究 酚类化合物的性质。 我们现建议把这项工作由 从相对简单的烷基酚到更复杂的化合物， 天然酚类的结构特征。 具体 目的如下：（1）研究过氧醌的贡献 单核细胞的微粒体和细胞代谢 含有邻甲氧基或间羟基取代基的酚，和 具有甲基取代基的多核酚。 确定雌激素是否 通过过氧喹啉途径氧化。 (2)识别形成的产品， 血红素蛋白降解过氧喹啉的途径。 用肝细胞色素P450和位点特异性突变体获得的数据 P450cam和肌红蛋白的结合将阐明血红素蛋白的机制， 提供关于过氧喹啉类生物活性产品的信息。 (3)过氧喹啉类化合物对大鼠肝细胞和小鼠肝细胞的影响 角质形成细胞 确定过氧喹啉介导的 非血红素蛋白中甲硫氨酸残基的氧化，并确定 DNA结合的金属离子将过氧喹啉还原为自由基物质， DNA. 实现这些具体目标将大大提高我们的 了解这种新的氧化途径及其介导 某些酚类化合物的生物效应。

There is a great deal of interest in naturally occurring phenols because of their enormous potential as agents for antioxidant therapy and cancer prevention. Unfortunately, however, these substances also lead to the formation of free radicals, mutations, tumors, and cytotoxicity. Mechanisms underlying the various biological effects of phenols must be elucidated before those factors which influence the blend of beneficial and determinant properties can be more fully understood. The metabolic activation of these compounds by cytochrome P450 involves well known reactive metabolites such as epoxides and quinones, but phenoxy radicals produced by P450-catalyzed one-electron oxidation can add molecular oxygen para to the hydroxy group to form hydroperoxy-cyclohexadienones, referred to in the chemical literature as 'peroxyquinols.' This novel pathway has not been widely recognized because peroxyquinols do not accumulate, but are rapidly degraded in biological systems. During the current funding period, it has been demonstrated, using a series of alkyl-substituted phenols, that peroxyquinol formation occurs to a significant extent both in liver microsomes and in isolated hepatocytes. The relative contribution of this pathway is influenced by the substrate structure and P450 isozyme. Peroxyquinols are rapidly degraded by various hemeproteins along complex pathways, form radicals and electrophilic products, selectively oxidize methionine residues of intact proteins, and severely damage cells. The data strongly support continued studies on the roles of peroxyquinols in mediating the biological properties of phenolic compounds. We now propose to extend the work from relatively simple alkylphenols to more complex compounds that contain structural features common to naturally occurring phenols. The specific aims are as follows: (1) Investigate the contribution of peroxyquinol formation to the microsomal and cellular metabolism of mononuclear phenols containing ortho-methoxy or meta-hydroxy substituents, and polynuclear phenols with methyl substituents. Determine if estrogens are oxidized via the peroxyquinol pathway. (2) Identify products formed and pathways involved in the degradation of peroxyquinols by hemeproteins. Data obtained with hepatic cytochromes P450, and site-specific mutants of P450cam and myoglobin will elucidate hemeprotein mechanisms, and provide information on biologically active products of peroxyquinols. (3) Study the effects of peroxyquinols on rat hepatocyte and murine keratinocytes. Determine the consequences of peroxyquinol-mediated oxidations of methionine residues in non-heme proteins, and determine if DNA-bound metal ions reduce peroxyquinols to radical species that damage DNA. Accomplishing these specific aims will significantly enhance our knowledge of this novel oxidative pathway and its potential to mediate the biological effects of certain phenolic compounds.