Moloney S J, Wiebkin P, Cummings S W, Prough R A
Carcinogenesis. 1985 Mar;6(3):397-401. doi: 10.1093/carcin/6.3.397.
The NADPH-dependent microsomal metabolism of [14C]procarbazine, labeled on the terminal N-methyl group, resulted in the covalent binding of the drug to exogenously added DNA; this reaction was inhibited by metyrapone. Procarbazine metabolism was also shown to result in covalent binding of the methyl group of the drug to microsomal protein upon metabolism, but the extent of protein binding was at least an order of magnitude smaller than that seen with its primary oxidative metabolite. N-isopropyl-alpha-(2-methylazo)-p-toluamide. The characteristics of the reactions leading to the covalent binding of the N-methyl group of the azo derivative to microsomal protein and its metabolism to form the hydrocarbon, methane, possessed a number of similarities in the apparent kinetic parameters (Km and Vmax), induction, and inhibition patterns indicating a common pathway of metabolism to form a reactive intermediate and the involvement of cytochrome P-450. Reduced glutathione stimulated methane formation and inhibited covalent binding to protein. One azoxy derivative, N-isopropyl-alpha-(2-methyl-ONN-azoxy)-p-toluamide, was chemically unstable and its decomposition was shown to lead to covalent binding to microsomal protein. A diazene intermediate and a methyl radical are proposed to be intermediates in the formation of methane during the oxidative metabolism of the azo derivative of procarbazine and a common intermediate in the activation of procarbazine may result in both covalent binding to cellular macromolecules and methane production. In addition, chemical decomposition of the azoxy metabolites may also contribute to a small portion of the covalent binding, but not to methane formation.
[14C]甲基苄肼在末端N-甲基处标记，其依赖烟酰胺腺嘌呤二核苷酸磷酸（NADPH）的微粒体代谢导致药物与外源添加的DNA发生共价结合；该反应被甲吡酮抑制。甲基苄肼代谢还显示，药物甲基在代谢后与微粒体蛋白发生共价结合，但其与蛋白的结合程度比其主要氧化代谢产物N-异丙基-α-（2-甲基偶氮）-对甲苯酰胺至少小一个数量级。偶氮衍生物的N-甲基与微粒体蛋白共价结合及其代谢形成碳氢化合物甲烷的反应特性，在表观动力学参数（Km和Vmax）、诱导和抑制模式方面有许多相似之处，表明形成反应性中间体的代谢途径相同，且涉及细胞色素P-450。还原型谷胱甘肽刺激甲烷生成并抑制与蛋白的共价结合。一种偶氮氧基衍生物N-异丙基-α-（2-甲基-ONN-偶氮氧基）-对甲苯酰胺化学性质不稳定，其分解导致与微粒体蛋白共价结合。在甲基苄肼偶氮衍生物的氧化代谢过程中，二氮烯中间体和甲基自由基被认为是甲烷形成的中间体，甲基苄肼激活过程中的共同中间体可能导致与细胞大分子的共价结合和甲烷生成。此外，偶氮氧基代谢产物的化学分解可能也会导致一小部分共价结合，但不会导致甲烷生成。
