Effects of Ce3+ on Conformation and Activity of Superoxide Dismutase

Ce 3+ in various concentrations was added to superoxide dismutase (SOD) from rat eryhrocyte in vitro to gain insight into the mechanism of molecular interactions between Ce 3+ and SOD. The results showed that the reaction between SOD and Ce 3 was two order, which meant that the SOD activity was markedly accelerated by a low concentration of Ce 3+ and inhibited by a high concentration of Ce 3+ . The spectroscopic assays suggested that the Ce 3+ was determined to directly bind to SOD; the binding site of Ce 3+ to SOD was 0.96, and the binding constants ( K A ) were 6.78 × 10 5 and 1.68 × 10 5 L·mol −1 ; the binding Ce 3+ 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.