Biosynthesis of Rat Kidney Catalase: Double-labeling by [¹⁴C]Leucine and δ-Amino ¹³Hilevulinic Acid

Abstract

Kidney catalase [EC 1.11.1.6] was doubly labeled by injecting a mixture of [¹⁴C]-leucine and δ-amino[³H]levulinic acid (ALA) into normal and allyliso-(2-isopropy1-4-pentenoyl)urea (Sedormid)-treated rats.

Shortly after the injection of a tracer dose of the precursors, catalase in micro-somes showed the highest specific radioactivities among catalases from various cell fractions. On the other hand, peroxisomal catalase was labeled gradually, reaching a plateau at about 90 min. The patterns of incorporation of both isotopes were similar to those obtained previously with rat live catalase, except that the ³H-radioactivities were much higher. From the results obtained it could be postulated that kidney catalase is synthesized on polysomes and then transferred to peroxisomes, directly or via the soluble phase.

The ratio of ³H/¹⁴C incorporated was lowest in microsomal catalase, highest in microsomal catalase, highest in peroxisomal enzyme and intermediate in catalase of the soluble fraction. The increment with time was large in the latter two catalases, while the former showed a rather small change. The evidence suggests that nascent catalase contains less heme than the completed molecule; further addition of heme to this intermediate seems to occur in the cytosol, and possibly also in peroxisomes.

Administration of a porphyrinogenic drug, (2-isopropyl-4-pentenoyl)urea, produced a remarkable decrease in the incorporation of [³H]ALA into kidney catalase, with no significant effect on that of [¹⁴C]leucine.