On the synthesis and degradation of the multiple forms of catalase in mouse liver

Aspects of the synthesis and degradation of the multiple forms of catalase in mouse liver have been investigated. The kinetics of return of catalase after aminotriazole inhibition indicated a product-precursor relationship between the granular and supernatant pools of the enzyme, and electrophoretic resolution of the individual heteromorphs of catalase during this treatment served to substantiate this relationship and indicated, in addition, that aminotriazole-inhibited catalase may be partially reactivated in the cytosol. Changes in the activity of mouse liver and kidney catalases after the administration of chlorophenoxyisobutyric acid ethyl ester (CPIB) were also monitored. After an initial decline in activity, a rapid increase to an elevated steady state occurred, with an approximately threefold increase in the liver and twofold increase in the kidney. Subcellular fractionation of the livers of CPIB-treated mice showed a massive initial increase in the supernatant pool of catalase, accompanied by a steady decrease in the activity of the peroxisomal pools. Activity increased in the peroxisomal pools at later stages of treatment, but even after a new CPIB-induced steady state was achieved, the supernatant pool of catalase remained grossly elevated. Electrophoresis of the individual heteromorphs of catalase in the supernatant after CPIB treatment showed a predominance of the most cathodal migrating forms, and turnover studies demonstrated that catalase in CPIB-treated animals exhibited a substantially lowered rate of degradation by comparison with normal animals. These results have been discussed in relation to the intracellular sequestration and turnover characteristics of catalase.