ENZYMATIC OXIDATION OF DRUGS TO TOXIC AND CARCINOGENIC METABOLITES

主要目标是阐明反应性的结构， 致癌、细胞毒性和致突变的代谢物 多环芳烃和其他化学品的活性 环境化学品。 采取的方法包括：一）研究 用肝微粒体和纯化的 细胞色素P450和环氧化物水解酶，ii）氧化 代谢物，iii）评价的致突变性和致肿瘤性 合成代谢物，iv）阐明细胞色素的作用 P450系统和环氧化物水解酶在调节这些突变中的作用 代谢物，v）测定以下物质的反应速率和产物： 芳烃氧化物和二醇环氧化物与生物聚合物和模型化合物，和 vi）寻找能够预防肿瘤的致瘤性的试剂， 活性代谢物。 过去一年的工作集中在两个方面： 地区 i）K区芳烃氧化物反应机理的研究 已经阐明了内在的化学反应性在每个 环氧碳 构象因子在细胞的生长过程中起着关键作用。 溶剂分解和环氧化物的速率和产物的测定 水解酶催化水解。 我们的研究结果还表明， 甲氧基离子亲核进攻K区的过渡态 芳烃氧化物（环氧化物水解酶催化水进攻的模型） 在碳上带有部分正电荷， 亲核取代 （二）综合研究产生了 含有特定二醇的生物学上有意义的寡核苷酸 环氧加合物。 一种加合物对应于反式打开的 (1R 2S）-二醇（3S，4 R）-环外氨基环氧化菲 的脱氧腺苷（dA）掺入到九核苷酸中，所述九核苷酸包含 人K-ras B癌基因的密码子60-62。 形成的双链体中， 加合寡核苷酸，脱氧鸟苷取代胸苷 在修饰的dA相对的互补链中几乎没有影响 在熔化温度上。 这一结果表明， 由二醇环氧化物加合物引起突变中的这种碱基对“错配 阵

The primary goal has been the elucidation of the structures of reactive metabolites responsible for the carcinogenic, cytotoxic and mutagenic activity of drugs, polycyclic aromatic hydrocarbons and other environmental chemicals. The approach taken consists of: i) study of the metabolism of the chemicals with liver microsomes and with purified cytochromes P450 and epoxide hydrolase, ii) synthesis of oxidative metabolites, iii) evaluation of the mutagenicity and tumorigenicity of the synthetic metabolites, iv) elucidation of the roles of the cytochrome P450 system and epoxide hydrolase in modulating the mutagenicity of these metabolites, v) determination of the rates and products of reactions of arene oxides and diol epoxides with biopolymers and model compounds, and vi) search for agents capable of preventing the tumorigenicity of reactive metabolites. Work during the past year has focused in two areas. i) Studies of the reaction mechanisms of K-region arene oxides have elucidated the role of the intrinsic chemical reactivity at each epoxide carbon. Conformational factors play a key role in the determination of rates and products of solvolytic cleavage and epoxide hydrolase-catalyzed hydrolysis. Our results also suggest that the transition state for nucleophilic attack of methoxide ion on the K-region arene oxides (a model for attack of water catalyzed by epoxide hydrolase) involves a partial positive charge on the carbon that undergoes nucleophilic substitution. ii) Synthetic studies have produced biologically significant oligonucleotides containing specific diol epoxide adducts. An adduct corresponding to trans opening of the (1R,2S)-diol (3S,4R)-epoxide of phenanthrene by the exocyclic amino group of deoxyadenosine (dA) was incorporated into a nonanucleotide comprising codons 60-62 of the human K-ras b oncogene. In duplexes formed by this adducted oligonucleotide, substitution of deoxyguanosine for thymidine in the complementary strand opposite the modified dA had almost no effect on the melting temperature. This result suggests a possible role for such base-pair "mismatches" in mutations caused by diol epoxide adduct formation.