Effect of γ-Rays on the Action of an Enzyme

Abstract

LITTLE is known about the effects of high energy radiation on the mechanism of enzyme action. Charlesby¹ investigated the decrease of activity of alcohol dehydrogenase irradiated with α- and γ-rays and found a relatively high resistance. We have been interested, however, in the effects on the reaction of enzymes such as alterations in reaction rates, specificity and structure of products. We chose to use dextran sucrase because this enzyme is available in relatively pure preparations² and its reaction mechanism is well known from this kind of kinetic work³. It is of advantage that dextran sucrase catalyses a poly reaction and the values of the molecular weights of the products are a further parameter of the reaction. Dextran sucrase from Leuconostoc mesenteroides B 512 F has been used, converting sucrose into fructose and high polymer dextran. The irradiations were carried out with a cobalt-60 source of about 20,000 c. First results showed that the radiation resistance of the enzyme depends a great deal on the purity of the preparation. In our experiments the enzyme concentration was between 12 and 50 U/ml. and iradiation usually lasted for 1 h.