Biological and Pharmaceutical Bulletin
Online ISSN : 1347-5215
Print ISSN : 0918-6158
ISSN-L : 0918-6158
Inhibitory Effect of Regucalcin on Ca2+/Calmodulin-Dependent Phosphatase Activity in Rat Renal Cortex Cytosol
Masami OMURAHideyuki KUROTAMasayoshi YAMAGUCHI
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1998 Volume 21 Issue 5 Pages 440-443

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Abstract
The effect of regucalcin, a Ca2+-binding protein, on Ca2+/calmodulin-dependent phosphatase activity in rat renal cortex cytosol was investigated. The addition of Ca2+/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 (10-6M) in the enzyme reaction mixture caused a complete inhibition of Ca2+/calmodulin-dependent phosphatase activity in renal cortex cytosol. A half miximum effect of regucalcin inhibition was seen at 10-8M concentration. Moreover, phosphatase activity of purified calcineurin was significantly enhanced by the addition of Ca2+/calmodilin. This enhancement was completely inhibited by the presence of regucalcin (10-7M). The inhibitory effect of regucalcin was not weakened by increasing concentrations of CaCl2 (10-6 to 10-4M). The present results suggest that regucalcin can inhibit Ca2+/calmodilin-dependent phosphatase activity in rat renal cortex.
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© The Pharmaceutical Society of Japan
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