Maeda H, Sato K, Akaike T
Department of Microbiology, Kumamoto University School of Medicine, Japan.
Princess Takamatsu Symp. 1995;23:103-12.
Highly purified cytochrome P-450 reductase (also called cytochrome C reductase; EC 1.6.2.4.) and NADPH were found to generate superoxide radical (O2.-) from 11 different heterocyclic amines (HCAs) as identified by electron spin resonance spectroscopy (ESR) using the spin trapping method with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). The signal intensity of DMPO-OOH(-O2.-) (i.e., the DMPO spin adduct of O2.-) was strongest for 2-amino-3,4-dimethylimidazo[4,5-f]-quinoline (MeIQ). O2.- generation with HCAs was decreased in the following order: 2-amino-3,8-dimethylimidazo[4,5-f]-quinoxaline (MeIQx) = 2-amino-3-methylimidazo[4,5-fl-quinoline (IQ) > 2-amino-3,4,8-trimethylimidazo[4,5-f]-quinoxaline (diMeIQx) > or = other HCAs; O2.- generation was lowest with 2-amino-3-methyl-9H-pyrido[2,3-b]indole-CH3COOH (MeA alpha C). By using Lineweaver-Burk plots, Km values of cytochrome P-450 reductase for mitomycin C, IQ, and MeIQ were determined to be 1.60 x 10(-6)M, 1.97 x 10(-5)M, and 2.83 x 10(-6) M, respectively. The N-hydroxyl derivative of 3-amino-1-methyl-5H-pyrido[4,3-b]-indole-HCI-CH3COOH (Trp-P-2), which is considered to be a key intermediate in the reaction of Trp-P-2 with cytochrome P-450 systems, yielded very little generation of O2.-. Because of the known presence of cytochrome P-450 reductase in the cell at significant amount, the present findings are an important implication for carcinogenesis and tumor promotion due to the known effect of oxygen radicals on promotion/progression, cell kill and proliferation.
利用5,5-二甲基-1-吡咯啉-N-氧化物（DMPO）自旋捕获法，通过电子自旋共振光谱（ESR）鉴定发现，高度纯化的细胞色素P-450还原酶（也称为细胞色素C还原酶；EC 1.6.2.4.）和NADPH可从11种不同的杂环胺（HCA）中产生超氧自由基（O2.-）。对于2-氨基-3,4-二甲基咪唑[4,5-f]喹啉（MeIQ），DMPO-OOH（-O2.-）（即O2.-的DMPO自旋加合物）的信号强度最强。HCA产生O2.-的能力按以下顺序降低：2-氨基-3,8-二甲基咪唑[4,5-f]喹喔啉（MeIQx） = 2-氨基-3-甲基咪唑[4,5-f]喹啉（IQ）> 2-氨基-3,4,8-三甲基咪唑[4,5-f]喹喔啉（二甲基MeIQx）>或 = 其他HCA；2-氨基-3-甲基-9H-吡啶并[2,3-b]吲哚-CH3COOH（MeAαC）产生O2.-的能力最低。通过使用Lineweaver-Burk图，确定细胞色素P-450还原酶对丝裂霉素C、IQ和MeIQ的Km值分别为1.60×10（-6）M、1.97×10（-5）M和2.83×10（-6）M。3-氨基-1-甲基-5H-吡啶并[4,3-b]吲哚-HCl-CH3COOH（Trp-P-2）的N-羟基衍生物被认为是Trp-P-2与细胞色素P-450系统反应的关键中间体，其产生的O2.-很少。由于已知细胞中存在大量细胞色素P-450还原酶，鉴于氧自由基对促进/进展、细胞杀伤和增殖的已知作用，目前的研究结果对致癌作用和肿瘤促进具有重要意义。
