不同金属辅基和酶剂量对超氧化物歧化酶抗氧化、促氧化作用的影响

研究含不同类型金属辅基(Mn或Cu,Zn)的超氧化物歧化酶(SOD)的抗氧化/促氧化作用特征,以及酶剂量对其抗氧化/促氧化作用的影响。用化学发光法分析超氧化物歧化酶对由Fenton体系产生的羟基自由基(.OH)导致DNA氧化损伤的影响。进一步利用.OH所致质粒DNA氧化后在琼脂糖凝胶电泳中的构型改变为实验模型,比较不同类型金属辅基和剂量对SOD抗氧化/促氧化活性的影响。Mn-SOD对.OH引起的DNA氧化损伤没有显著影响。然而,Cu,Zn-SOD在较高浓度(>200 U/ml)下,表现出强烈的促氧化效应,能够加剧DNA氧化损伤。研究结果表明,金属辅基对SOD的抗氧化或促氧化效应有着重要的影响,这可能与金属辅基在Fenton反应中的氧化还原特性相关。高浓度的Cu,Zn-SOD对.OH所致DNA氧化损伤存在显著的促氧化效应。高浓度的Mn辅基离子不能与Fenton体系中H2O2直接作用,并且不能促进羟基自由基的形成。

EFFECTS OF DIFFERENT METAL PROSTHETIC GROUPS AND CONCENTRATION ON ANTIOXIDANT AND PROOXIDANT ACTIVITIES OF SUPEROXIDE DISMUTASE

A study was carried out to make an understanding of theantioxidant or prooxidant effect of Mn-SODand Cu,Zn-SOD,and to analyze the effects of SOD at various concentrations on DNA oxidative damage.Effects of SOD on hydroxyl radical induced DNA oxidative damage were measured by using chemiluminescence method.With agarose gel electrophoresis,antioxidant or prooxidant effect of different types of SOD(Cu,Zn-SOD and Mn-SOD) was studied by analyzing the ratio of SC(supercoiled)form of pBR322.Results show that Mn-SOD has no effects on hydroxyl radical-induced DNA.CAT shows protective effect on DNA with concentration dependence.On the other hand,Cu,Zn-SOD at high concentrations(>200 U/ml)exhibits a significant prooxidant effect on DNA,and enhances DNA damage.Prosthetic group has important effects on antioxidant or prooxidant activity of SOD.This maybe due to redox character of different metal ions in Fenton reaction.Cu,Zn-SOD at higher concentration has remarkable prooxidant effect on DNA.Mn ions of Mn-SOD at higher concentration would not react with H_2O_2 in Fenton system and have no effects on DNA damage.