[Radiation inactivation of alpha-chymotrypsin in aqueous solutions. Effect of irradiation conditions].

A comparative study was made of inactivation by gamma- and beta-radiation of alpha-chymotrypsin within a wide range of its initial concentrations (from 10(-4) to 10(-7) M). The regularities of gamma- and beta-inactivation are the same, and distinctions, if any, are due to a greater radiation effect of beta-rays on dilute enzyme solutions (less than or equal to 5 X 10(-6) M). The inactivation of alpha-chymotrypsin by radiation proceeds either via primary molecule unfolding followed by degradation of the most accessible and radiosensitive amino acid residues (pH 7.8) or, to a greater extent, via direct disruption of amino acid residues which can probably be random (pH 3.0). Calcium ions stabilize, on the whole, the enzyme molecule upon irradiation.