Clejan L A, Cederbaum A I
Department of Biochemistry, Mount Sinai School of Medicine, New York, NY 10029.
Biochem J. 1993 Nov 1;295 ( Pt 3)(Pt 3):781-6. doi: 10.1042/bj2950781.
Glycerol can be oxidized to formaldehyde by microsomes in a reaction that is dependent on cytochrome P-450. An oxidant derived from the interaction of H2O2 with iron was responsible for oxidizing the glycerol, with P-450 suggested to be necessary to produce H2O2 and reduce non-haem iron. The effect of paraquat on formaldehyde production from glycerol and whether paraquat could replace P-450 in supporting this reaction were studied. Paraquat increased NADPH-dependent microsomal oxidation of glycerol; the stimulation was inhibited by glutathione, catalase, EDTA and desferrioxamine, but not by superoxide dismutase or hydroxyl-radical scavengers. The paraquat stimulation was also inhibited by inhibitors, substrate and ligand for P-4502E1 (pyrazole-induced P-450 isozyme), as well as by anti-(P-4502E1) IgG. These results suggest that P-450 still played an important role in glycerol oxidation, even in the presence of paraquat. Purified NADPH-cytochrome P-450 reductase did not oxidize glycerol to formaldehyde; some oxidation, however, did occur in the presence of paraquat. Reductase plus P-4502E1 oxidized glycerol, and a large stimulation was observed in the presence of paraquat. Rates in the presence of P-450, reductase and paraquat were more than additive than the sums from the reductase plus P-450 and reductase plus paraquat rates, suggesting synergistic interactions between paraquat and P-450. These results indicate that paraquat increases oxidation of glycerol to formaldehyde by microsomes and reconstituted systems, that H2O2 and iron play a role in the overall reaction, and that paraquat can substitute, in part, for P-450 in supporting oxidation of glycerol. However, cytochrome P-450 is required for elevated rates of formaldehyde production even in the presence of paraquat.
甘油可被微粒体氧化为甲醛，此反应依赖于细胞色素P - 450。由过氧化氢与铁相互作用产生的一种氧化剂负责氧化甘油，推测P - 450对于产生过氧化氢和还原非血红素铁是必需的。研究了百草枯对甘油生成甲醛的影响以及百草枯是否能替代P - 450来支持该反应。百草枯增加了微粒体对甘油的NADPH依赖性氧化；这种刺激被谷胱甘肽、过氧化氢酶、EDTA和去铁胺抑制，但不被超氧化物歧化酶或羟基自由基清除剂抑制。百草枯的刺激作用也被P - 4502E1（吡唑诱导的P - 450同工酶）的抑制剂、底物和配体以及抗 - (P - 4502E1) IgG抑制。这些结果表明，即使在有百草枯存在的情况下，P - 450在甘油氧化中仍起重要作用。纯化的NADPH - 细胞色素P - 450还原酶不能将甘油氧化为甲醛；然而，在有百草枯存在的情况下确实发生了一些氧化反应。还原酶加P - 4502E1可氧化甘油，并且在有百草枯存在时观察到了显著的刺激作用。在有P - 450、还原酶和百草枯存在时的反应速率比还原酶加P - 450以及还原酶加百草枯的速率之和更具加和性，表明百草枯与P - 450之间存在协同相互作用。这些结果表明，百草枯增加了微粒体和重组系统将甘油氧化为甲醛的能力，过氧化氢和铁在整个反应中起作用，并且百草枯在支持甘油氧化方面可部分替代P - 450。然而，即使在有百草枯存在的情况下，甲醛生成速率升高仍需要细胞色素P - 450。
