Some effects of ionizing radiations on the alkaline phosphatase in cow's milk

Abstract

SummaryThe effects of ionizing radiation on the alkaline phosphatase activity of milk have been studied under different environmental conditions. Twenty-five megarads were required to inactivate the enzyme completely. A combination of heat treatment and irradiation given either before or after heating showed that inactivation of the enzyme was greater when heating occurred after irradiation, this effect of the different forms of energy possibly indicating different mechanisms of heat inactivation. Varying the dose rate over the range 12–250 krad/min did not affect the amount of enzyme inactivated. After irradiation, activity declined during storage at 30°C but not at 5°C. Irradiation did not change the value ofKmyet theVmaxfell, indicating that there are fewer active sites present after irradiation but that affinity of the remaining sites for the substrate remains unchanged.