抄録
The mechanism of inactivation of papain by ascorbic acid in the presence of cupric ions was investigated. Dehydroascorbic acid and hydrogen peroxide which were oxidative product of ascorbic acid, were much less effective. In addition, bubbling nitrogen gas and radical scavengers prevented the inactivation by ascorbic acid and cupric ions. The results indicated that the inactivating effect of ascorbic acid was oxygen dependent and caused by free radicals formed during the autoxidation of ascorbic acid. The N-terminal amino acid and polyacrylamide disc gel electrophoretical patterns of the inactivated papain did not so differ from those of the native papain. On the other hand, the amino acids composition and fluorescence spectrum were changed in the inactivated papain as compared with the intact papain. These facts suggest that the cleavage of the S-S bond of papain molecule produced by the treatment with ascorbic acid and cupric ions resulted in inactivation.