Studies on catalase compartmentation in digitonin-treated rat hepatocytes

The cellular compartmentation of catalase was studied in digitonin-permeabilized rat hepatocytes. A biphasic dose-response curve was observed for the unmasking of catalase activity by digitonin in latency studies. About 40-60% of the total catalase activity was seen in the range of 5-200 microM digitonin compared to 13% free activity in control preparations without digitonin. The free catalase activity began to increase again above 300 micron digitonin, and all latency was lost around 500 microM and above. These results indicate that there exists in rat hepatocytes catalase with two levels of crypticity to digitonin, only one of which was seen in a mixed organelle preparation containing peroxisomes.