Dudley B F, Winston G W
Department of Biochemistry, Louisiana State University, Baton Rouge 70803.
Arch Biochem Biophys. 1995 Feb 1;316(2):879-85. doi: 10.1006/abbi.1995.1118.
Liver cytosolic fractions are known to catalyze the reduction of certain C-nitroso compounds to their corresponding hydroxylamines and amines. Alcohol dehydrogenase (ADH), NAD(P)H:quinone oxidoreductase, and xanthine and aldehyde oxidases have been implicated as C-nitroso reductases. To probe the role of these cytosolic enzymes in the reduction of C-nitroso compounds we have studied the effects of classical inhibitors of these enzymes on the ability of liver cytosolic fractions from ADH+ and ADH- deermice to reduce p-nitrosophenol to p-aminophenol. Pyrazole, a potent inhibitor of ADH, inhibited NADH-p-nitrosophenol reduction by ADH+ cytosol by > 85%. Thus, ADH contributes substantially to NADH-C-nitroso reduction by cytosol from ADH+ deermice. The NAD(P)H:quinone oxidoreductase inhibitor, dicumarol, inhibited NADH-dependent p-aminophenol formation by about 25%; however, dicumarol potently inhibited the NADPH-dependent formation (90-95%). As expected, cytosol from ADH- deermice did not catalyze pyrazole-sensitive (ADH-dependent) C-nitroso reduction with NADH as the cofactor. Both NADPH- and NADH-p-nitrosophenol reduction by ADH- cytosol were inhibited > 90% by dicumarol. The xanthine oxidase/aldehyde oxidase inhibitor, allopurinol, was without effect on NAD(P)H cytosolic p-nitrosophenol reduction from ADH- and ADH+ deermice under either aerobic or anaerobic conditions. Our findings suggest that in the ADH+ animal, ADH contributes significantly to NADH-dependent C-nitroso reduction by cytosol relative to NAD(P)H:quinone oxidoreductase. NADPH-dependent p-nitrosophenol reduction by liver cytosol of ADH+ animals is mostly dicumarol-sensitive, which implicates NAD(P)H:quinone oxidoreductase as the major NADPH-dependent activity. In ADH- deermice, both NADH- and NADPH-dependent p-nitrosophenol reduction are essentially dicumarol-sensitive (NAD(P)H:quinone oxidoreductase-dependent). Because the toxic expression of C-nitroso compounds is mediated by hydroxylamine intermediates, the present data indicate the importance of considering the role of ADH in the toxic sequelae of nitro and nitroso arenes.
已知肝脏胞质部分能催化某些C-亚硝基化合物还原为相应的羟胺和胺。乙醇脱氢酶（ADH）、NAD(P)H：醌氧化还原酶以及黄嘌呤氧化酶和醛氧化酶被认为是C-亚硝基还原酶。为了探究这些胞质酶在C-亚硝基化合物还原中的作用，我们研究了这些酶的经典抑制剂对ADH+和ADH-鹿鼠肝脏胞质部分将对亚硝基苯酚还原为对氨基苯酚能力的影响。吡唑是一种有效的ADH抑制剂，它抑制ADH+胞质溶胶中NADH-对亚硝基苯酚的还原超过85%。因此，ADH对ADH+鹿鼠胞质溶胶中NADH-C-亚硝基还原有很大贡献。NAD(P)H：醌氧化还原酶抑制剂双香豆素抑制NADH依赖性对氨基苯酚的形成约25%；然而，双香豆素强烈抑制NADPH依赖性的形成（90-95%）。正如预期的那样，ADH-鹿鼠的胞质溶胶在以NADH作为辅因子时，不催化吡唑敏感的（ADH依赖性的）C-亚硝基还原。双香豆素对ADH-胞质溶胶中NADPH-和NADH-对亚硝基苯酚的还原均有>90%的抑制作用。黄嘌呤氧化酶/醛氧化酶抑制剂别嘌呤醇在有氧或无氧条件下，对ADH-和ADH+鹿鼠的NAD(P)H胞质对亚硝基苯酚还原均无影响。我们的研究结果表明，在ADH+动物中，相对于NAD(P)H：醌氧化还原酶，ADH对胞质溶胶中NADH依赖性C-亚硝基还原有显著贡献。ADH+动物肝脏胞质溶胶中NADPH依赖性对亚硝基苯酚的还原大多对双香豆素敏感，这表明NAD(P)H：醌氧化还原酶是主要的NADPH依赖性活性。在ADH-鹿鼠中，NADH-和NADPH依赖性对亚硝基苯酚的还原基本上都对双香豆素敏感（NAD(P)H：醌氧化还原酶依赖性）。由于C-亚硝基化合物的毒性表达是由羟胺中间体介导的，目前的数据表明在考虑硝基和亚硝基芳烃的毒性后遗症时，ADH的作用很重要。
