Kukiełka E, Cederbaum A I
Department of Biochemistry, Mount Sinai School of Medicine, New York, NY 10029.
Drug Metab Dispos. 1991 Nov-Dec;19(6):1108-15.
Rat liver microsomes oxidized ethylene glycol to formaldehyde in a NADPH-dependent, carbon monoxide-sensitive manner. Formaldehyde production was inhibited by substrates and ligands for cytochrome P-450 such as aniline, p-nitrophenol, pyrazole, and 4-methylpyrazole, and inhibitors such as tryptamine, cimetidine, and miconazole. The apparent Km for ethylene glycol was about 25 mM and the apparent Vmax was about 6 nmol/min/mg protein. Microsomes isolated from rats treated with pyrazole or 4-methylpyrazole to induce cytochrome P-450IIE1 oxidized ethylene glycol at rates which were about twice those found with control microsomes or microsomes isolated from rats treated with phenobarbital or 3-methylcholanthrene, although significant rates were found with all microsomal preparations. Antibody raised against the pyrazole-induced P-450IIE1 inhibited formaldehyde production from ethylene glycol in microsomes from pyrazole-treated rats. H2O2 itself did not oxidize ethylene glycol to formaldehyde; however, the microsomal reaction was inhibited by catalase or glutathione plus glutathione peroxidase and was stimulated by added H2O2 in the presence of NADPH. Nonheme iron also appeared to be required for ethylene glycol oxidation in view of the inhibition of formaldehyde production by desferrioxamine, EDTA, and DTPA. Microsomal oxidation of ethylene glycol was not sensitive to superoxide dismutase, hydroxyl radical scavengers, or Trolox, suggesting that the oxidant derived from H2O2 and iron and responsible for the production of formaldehyde from ethylene glycol was not superoxide, hydroxyl radical, or lipid hydroperoxide. These results suggest that ethylene glycol is oxidized to formaldehyde by an oxidant derived from H2O2 and nonheme iron, and that cytochrome P-450 may function to generate the H2O2 and to catalyze reduction of the nonheme iron.
大鼠肝脏微粒体以NADPH依赖且对一氧化碳敏感的方式将乙二醇氧化为甲醛。甲醛的生成受到细胞色素P - 450的底物和配体（如苯胺、对硝基苯酚、吡唑和4 - 甲基吡唑）以及抑制剂（如色胺、西咪替丁和咪康唑）的抑制。乙二醇的表观Km约为25 mM，表观Vmax约为6 nmol/分钟/毫克蛋白。从用吡唑或4 - 甲基吡唑处理以诱导细胞色素P - 450IIE1的大鼠中分离出的微粒体氧化乙二醇的速率约为对照微粒体或从用苯巴比妥或3 - 甲基胆蒽处理的大鼠中分离出的微粒体的两倍，不过所有微粒体制剂都有显著的氧化速率。针对吡唑诱导的P - 450IIE1产生的抗体抑制了吡唑处理大鼠微粒体中乙二醇生成甲醛的反应。H2O2本身不会将乙二醇氧化为甲醛；然而，微粒体反应受到过氧化氢酶或谷胱甘肽加谷胱甘肽过氧化物酶的抑制，并且在有NADPH存在时，添加H2O2会刺激该反应。鉴于去铁胺、EDTA和DTPA对甲醛生成的抑制作用，非血红素铁似乎也是乙二醇氧化所必需的。乙二醇的微粒体氧化对超氧化物歧化酶、羟基自由基清除剂或Trolox不敏感，这表明由H2O2和铁产生的、负责将乙二醇氧化为甲醛的氧化剂不是超氧化物、羟基自由基或脂质过氧化氢。这些结果表明，乙二醇被由H2O2和非血红素铁产生的氧化剂氧化为甲醛，并且细胞色素P - 450可能起到生成H2O2和催化非血红素铁还原的作用。
