Protection of Catalase from Radiation-inactivation by Adenosine and its Derivatives in Dilute Solution

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Aqueous solutions of catalase were irradiated with ⁶⁰Co gamma-ray. Protective action of adenosine and its derivatives was examined under the conditions where the yield of the enzyme inactivation was independent upon the initial concentration of the enzyme. By increasing the concentration of the protective substance, a maximal protection was observed. The level of the maximum was dependent on the chemical structure of the protective substances. Addition of excess amounts of adenosine decreased the effectiveness of its N₆-hydroxyethyl derivative which was more protective, by itself, than adenosine. Based upon these observation, it was assumed that the binding of the protective substance to the enzyme molecule was the basis of the protection of the enzyme.