Pressure Effect on Thermal Inactivation of Calf Intestine Alkaline Phosphatase

Abstract

The pressure effects on thermal inactivation of calf intestine alkaline phosphatase (CIAP) have been studied by measuring the rate of hydrolysis of p-nitrophenyl phosphate (pNPP) catalyzed by CIAP in the temperature range of 25～60 ℃ and at the pressures up to 150 MPa. The apparent rate of hydrolysis decreased with time above a certain temperature. The decrease is due to the decrease in CIAP activity. The enthalpy change of the thermal inactivation was 354～478 kJ mol^-1, and volume change of this process was 8.8～40 cm³mol^-1. The mechanism of the thermal inactivation of CIAP is discussed in terms of each thermodynamic parameters.