Divalent Metal Ion-activated DNA Cleavage Activity of Copper Superoxide Dismutase

The study examined the DNA cleavage activity mediated by each member of the Cu2+-containing forms of CuZnSOD(CunSOD,n=1～4) in the presence of exogenous Mg2+ or Mn2+.The result indicates that upon addition of Mg2+ or Mn2+,CunSOD can more efficiently cleave DNA via a hydrolytic pathway compared with its holo and apo-forms.The factors,such as exogenous divalent metal concentration,pH and enzyme concentration,can affect the DNA cleavage activity.We also measured the relative enzyme activity and the steady state kinetic parameters of the DNA cleavage reaction,indicating that the DNA cleavage activity is independent of Cu2+ number in CunSOD,and increased in an order of Cu1SODCu2SOD≈Cu4SODCu3SOD.