Identification and subcellular localization of catalase activity in bovine adrenal medulla and cortex

Catalase activity was detected in homogenates of bovine adrenal cortex and medulla. Analysis by equilibrium density centrifugation in isoosmotic metrizamide-sucrose gradients revealed that 70% of the medullary catalase activity was soluble while most of the remainder was found in a particulate form with a density of 1.175 g/ml. This was distinct from the densities of lysosomes, mitochondria, and chromaffin granules. Catalase activity in adrenal cortex was primarily (90%) soluble with only 6% being particulate, with a density of 1.185 g/ml. d-Amino acid, uric acid, and α-hydroxyacid oxidase activities, often associated with peroxisomes in other tissues, were absent from homogenates and catalase-containing gradient fractions from either cortex or medulla. There was an indication that some catalase activity was associated with chromaffin granules on the basis of density gradient analysis of both medullary homogenates and crude granule preparations. When granule fractions were subjected to osmotic shock, catalase activity distributed between soluble and sedimentable fractions differently from epinephrine and dopamine β-hydroxylase activity. The sedimentable catalase activity remained associated with chromaffin granule membranes upon isopycnic centrifugation. We concluded that catalase activity in both adrenal cortex and medulla was largely cytoplasmic, but that both tissues contained at least some catalase in dense organelles. Catalase activity which may be associated with chromaffin granules represents a small fraction of the total activity in the medulla.