Effects of Cysteine and 4-Amino-1-Naphthol on Solutions of Lysosomal Enzymes Exposed to High Doses of Radiation

The effect of γ-irradiation on the lysosomal enzymes (acid phosphatase, DNase, RNase, β-galactosidase, β-glucuronidase, muramidase, and arylsulfatase) in the absence and in the presence of cysteine or 4-amino-1-naphthol (4A1N) was studied. Inactivation of these enzymes in the absence of the radioprotectors, cysteine and 4A1N, followed first-order kinetics. Muramidase was the most radiosensitive of all enzymes, having a D₃₇ value of 4 krads, whereas acid phosphatase was the most resistant, having a D₃₇ of 290 krads. Cysteine (0.1 mM) exerted no radioprotective effect on β-glucuronidase, the D₃₇ decreasing by 4 krads, whereas β-galactosidase was slightly protected, the D₃₇ increasing by 3 krads. The following enzymes were markedly protected: arylsulfatase, D₃₇ increased by 8 krads; muramidase, increased by 9 krads; DNase, increased by 13 krads; acid phosphatase, increased by 360 ...