Inhibitory Effect of Regucalcin on Ca^<2+>/Calmodulin-Dependent Phosphatase Activity in Rat Renal Cortex Cytosol

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The effect of regucalcin, a Ca^<2+>-binding protein, on Ca^<2+>/calmodulin-dependent phosphatase activity in rat renal cortex cytosol was investigated. The addition of Ca^<2+>/calmodulin in the enzyme reaction mixture caused a significant increase in the dephosphorylation of p-nitrophenylphosphate and phosphotyrosine used as the substrate for phosphatase in rat renal cortex cytosol. The presence of regucalcin (10^<-6>M) in the enzyme reaction mixture caused a complete inhibition of Ca^<2+>/calmodulin-dependent phosphatase activity in renal cortex cytosol. A half miximum effect of regucalcin inhibition was seen at 10^<-8>M concentration. Moreover, phosphatase activity of purified calcineurin was significantly enhanced by the addition of Ca^<2+>/calmodilin. This enhancement was completely inhibited by the presence of regucalcin (10^<-7>M). The inhibitory effect of regucalcin was not weakened by increasing concentrations of CaCl_2 (10^<-6> to 10^<-4>M). The present results suggest that regucalcin can inhibit Ca^<2+>/calmodilin-dependent phosphatase activity in rat renal cortex.
公益社団法人日本薬学会の論文
1998-05-15