[Inactivation and degradation of rat liver catalase by mitochondrial and lysosomal proteinases].

The initial phases of catalase degradation in rat hepatocytes were studied. Preparations of highly purified fractions of lysosomes and mitochondria from rat liver were obtained. The proteinase activity was measured by the radio-isotope method by the increase of the free amino groups or by the decrease of the catalase activity, using labelled catalase as a substrate. It was found that the initial step of catalase degradation occurs in the enzyme localized in the inner membrane as well as in the mitochondrial matrix and that the total degradation of catalase is completed in the lysosomal fraction of rat liver.