Abstract:Phosphoenolpyruvate (PEP) specific phosphatase was isolated from rice (Oryza sativa) leaves. Its Km (PEP) was 0. 42 mmol/L. The partially purified PEP phosphatase showed a narrow pH profile and had an optimum pH of 8.7. It was relatively stable at the pH ranging from 6.2 to 9.5 and at temperature below 40℃. Pi showed no effect on the enzyme activity at low concentrations, but slight inhibitory effect at the concentrations above 5 mmol/L. The enzyme activity was activated by Mgz+ and inhibited by CaCl2, CoCl2, CuSO4, FeSO4 and ZnSO4.