Biosynthesis of liver catalase in rats treated with allylisopropylacetylcarbamide. III. Occurrence of a possible precursor to catalase.

: Inactive catalase [EC 1.11.1.6] occurring in considerable amounts in liver peroxisomal extracts from Sedormid-treated rats was investigated. The antigen-to-enzyme ratio (i.e. the ratio of catalase determined immunochemically to catalase determined enzymatically; 1.0 for purified enzyme) was around 1.7 when peroxisomal extract from Sedormid-treated rats was assayed. After dialysis of the extract against a solution containing 44 mM acetate buffer, pH 4.1, and 22% ethanol, catalase remaining in soluble from showed the same antigen-to-enzyme ratio as the purified enzyme (1.0). Moreover, the total enzymatic activity was not reduced. The results indicated that the catalase precipitated by this treatment was enzymatically inactive. The peroxisomal extract was analyzed by gel filtration, and an enzymatically inactive catalase was detected in the region corresponding to molecules smaller than the enzymatically active catalase (tetramer). When the immunoprecipitates of the inactive catalase were analyzed by polyacrylamide gel electrophoresis in the presence of SDS and urea, only a subunit (monomer) of catalase was detected. At 60 min after injection of [14C]amino acid and delta-[3H]aminolevulinic acid into rats, the specific radioactivity of 14C in this inactive catalase was 6-7 times that of active catalase. On the other hand, the 3H/14C ratio was much lower than that of active catalase. The results suggest that the inactive catalase isolated by gel filtration is an intermediate of maturation, in which apo-catalase monomer binds with heme and assembles to form complete molecules.