Hashimoto F, Hayashi H
Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Josai University, Saitama.
J Biochem. 1990 Sep;108(3):426-31. doi: 10.1093/oxfordjournals.jbchem.a123217.
To clarify the significance of catalase in peroxisomes, we have examined the effect of aminotriazole treatment of rats on the activity of beta-hydroxybutyryl-CoA dehydrogenase in liver peroxisomes. When the effect of H2O2 on the dehydrogenase activity was examined using an extract of liver peroxisomes from aminotriazole-treated rats, the acetoacetyl-CoA-dependent oxidation of NADH was found to increase considerably on the addition of dilute H2O2. Such an effect of H2O2 was not seen on the beta-hydroxybutyryl-CoA-dependent reduction of NAD nor with extracts from untreated animals. We then noticed that similar NADH oxidation was caused non-enzymatically by a mixture of acetoacetyl-CoA and H2O2. The oxidation was dependent on both acetoacetyl-CoA and H2O2, and was blocked by scavengers of oxyradicals such as ascorbate and ethanol. Degradation products formed during the reaction of acetoacetyl-CoA with H2O2 had no NADH oxidizing activity, indicating that effective oxidant(s) were generated during the reaction of H2O2 with acetoacetyl-CoA. No other fatty acyl-CoA so far examined nor acetoacetate could replace acetoacetyl-CoA in this reaction. Therefore, if H2O2 were to be accumulated in peroxisomes, it would decrease both NADH and acetoacetyl-CoA, thus affecting the fatty acyl-CoA beta-oxidation system. These results, together with our previous finding that peroxisomal thiolase was significantly inactivated by H2O2 [Hashimoto, F. & Hayashi, H. (1987) Biochim. Biophys. Acta 921, 142-150] suggest that the role of catalase in peroxisomes is at least in part to protect the fatty acyl-CoA beta-oxidation system from the deleterious action of H2O2.
为阐明过氧化氢酶在过氧化物酶体中的意义，我们研究了用氨基三唑处理大鼠对肝脏过氧化物酶体中β-羟基丁酰辅酶A脱氢酶活性的影响。当使用来自氨基三唑处理大鼠的肝脏过氧化物酶体提取物检测H2O2对脱氢酶活性的影响时，发现加入稀H2O2后，NADH的乙酰乙酰辅酶A依赖性氧化显著增加。H2O2对NAD的β-羟基丁酰辅酶A依赖性还原没有这种作用，对未处理动物的提取物也没有这种作用。然后我们注意到，乙酰乙酰辅酶A和H2O2的混合物可非酶促地引起类似的NADH氧化。这种氧化依赖于乙酰乙酰辅酶A和H2O2，并被抗坏血酸和乙醇等氧自由基清除剂所阻断。乙酰乙酰辅酶A与H2O2反应过程中形成的降解产物没有NADH氧化活性，这表明H2O2与乙酰乙酰辅酶A反应过程中产生了有效的氧化剂。到目前为止，所检测的其他脂肪酰辅酶A和乙酰乙酸在该反应中均不能替代乙酰乙酰辅酶A。因此，如果H2O2在过氧化物酶体中积累，它将降低NADH和乙酰乙酰辅酶A，从而影响脂肪酰辅酶Aβ-氧化系统。这些结果，连同我们之前的发现，即过氧化物酶体硫解酶被H2O2显著灭活[桥本，F.和林，H.（1987年）生物化学与生物物理学报921，142 - 150]表明，过氧化氢酶在过氧化物酶体中的作用至少部分是保护脂肪酰辅酶Aβ-氧化系统免受H2O2的有害作用。
