Summary
Losses in enzyme activity and sulphydryl content have been studied in aerated papain solutions containing formate, superoxide dismutase and dithiothreitol. Both formate and dithiothreitol converted ·OH to ·O2−, whereas superoxide dismutase completely suppressed the inactivation by ·O2−. Using results from all three systems, the fraction of ·O2− reactions with papain that caused inactivation of the enzyme was 0·33 ± 0·07. The results also showed that the fraction of ·OH reactions, which cause inactivation of papain, is significantly higher in aerated than in oxygen-free solutions.