Effects of Ce3+ on conformation and activity of superoxide dismutase

Ce3+ in various concentrations was added to superoxide dismutase (SOD) from rat eryhrocyte in vitro to gain insight into the mechanism of molecular interactions between Ce3+ and SOD. The results showed that the reaction between SOD and Ce3 was two order, which meant that the SOD activity was markedly accelerated by a low concentration of Ce3+ and inhibited by a high concentration of Ce3+. The spectroscopic assays suggested that the Ce3+ was determined to directly bind to SOD; the binding site of Ce3+ to SOD was 0.96, and the binding constants (K(A)) were 6.78 x 10(5) and 1.68 x 10(5)L.mol(-1); the binding Ce3+ entirely altered the secondary structure of SOD. It implied that the Ce(3+) coordination created a new metal ion-active site form in SOD, thus leading to an enhancement in SOD activity.