Tomasz M, Chawla A K, Lipman R
Department of Chemistry, Hunter College, City University of New York, New York 10021.
Biochemistry. 1988 May 3;27(9):3182-7. doi: 10.1021/bi00409a009.
The relative amounts of monofunctional and bifunctional alkylation products of DNA with mitomycin C (MC) depend on whether one or both masked alkylating functions of MC are activated reductively; adduct 8 is the result of one function and adducts 7 and 9, formed as a pair, are the result of both functions being activated [Tomasz, M., Lipman, R., Chowdary, C., Pawlak, J., Verdine, G. L., & Nakanishi, K. (1987) Science (Washington, D.C.) 235, 1204-1208]. To determine the mechanism governing this differential reactivity of MC with DNA, MC-Micrococcus luteus DNA complexes formed under varying conditions in vitro were digested to nucleosides and adducts. Adduct distribution, analyzed by high-performance liquid chromatography, served as the measure of monofunctional and bifunctional activation. H2/PtO2 and xanthine oxidase/reduced nicotinamide adenine dinucleotide (NADH) activated MC mostly monofunctionally, and Na2S2O4 activated the drug bifunctionally under comparable conditions. Excess MC selectively suppressed, but excess PtO2 selectively promoted, bifunctional activation by H2/PtO2; excess xanthine oxidase and/or NADH also had promoting effects. O2 tested in the Na2S2O4 system was inhibitory. 10-Decarbamoyl-MC acted strictly monofunctionally under all conditions. Monoadducts bound to DNA were converted to bis adducts upon rereduction. A mechanism with the following features was derived: (i) Activation of MC at C-1 and C-10 is sequential (C-1 first). (ii) A one-time reduction is sufficient for both. (iii) Activation of the second function may be selectively inhibited by kinetic factors or O2. (iv) 7 and 9 are coproducts of bifunctional activation; their ratio depends on the DNA base sequence. (v) Activation of the second function involves an iminium intermediate. Direct applications to the action of MC in vivo are discussed.
丝裂霉素C（MC）与DNA形成的单功能和双功能烷基化产物的相对量，取决于MC的一个或两个被掩盖的烷基化功能是否被还原激活；加合物8是一个功能的结果，而成对形成的加合物7和9是两个功能都被激活的结果[托马什，M.，利普曼，R.，乔达里，C.，帕夫拉克，J.，韦尔迪内，G.L.，&中岸，K.（1987年）《科学》（华盛顿特区）235，1204 - 1208]。为了确定控制MC与DNA这种差异反应性的机制，将在体外不同条件下形成的MC - 藤黄微球菌DNA复合物消化为核苷和加合物。通过高效液相色谱分析加合物分布，作为单功能和双功能激活的度量。H2/PtO2和黄嘌呤氧化酶/还原型烟酰胺腺嘌呤二核苷酸（NADH）主要将MC单功能激活，而Na2S2O4在可比条件下将该药物双功能激活。过量的MC选择性抑制，但过量的PtO2选择性促进H2/PtO2的双功能激活；过量的黄嘌呤氧化酶和/或NADH也有促进作用。在Na2S2O4体系中测试的O2具有抑制作用。10 - 脱氨甲酰 - MC在所有条件下都严格单功能起作用。与DNA结合的单加合物在再还原时转化为双加合物。得出了具有以下特征的机制：（i）MC在C - 1和C - 10处的激活是顺序性的（C - 1先被激活）。（ii）一次还原对两者都足够。（iii）第二个功能的激活可能被动力学因素或O2选择性抑制。（iv）7和9是双功能激活的共产物；它们的比例取决于DNA碱基序列。（v）第二个功能的激活涉及亚胺鎓中间体。讨论了其在MC体内作用的直接应用。
