A low catalase activity in dog erythrocytes is due to a very low content of catalase protein despite having a normal specific activity.

Catalase was purified to an apparent homogeneity from dog erythrocytes and its properties were compared with those of human erythrocyte catalase. Purification was unsuccessful without the use of glycerol as the stabilizing agent. Molecular weight of the purified dog catalase was estimated to be about 63,000 Da in monomer and about 230,000 Da in native tetramer form. The ratio of A405/A280, the index of hematin content relative to protein, was 1.15. The isoelectric point was in the range of 5.8 to 6.4. These properties of dog catalase were very similar to those of human catalase. Dog catalase also possessed the same partial amino acid sequence as human catalase. However, the specific activity of dog enzyme was about threefold less than that of human enzyme. The amount of catalase protein in dog erythrocytes determined by immunoblotting analysis was about tenfold less than that of human erythrocytes. This was consistent with the fact that the catalase activity in dog hemolysate was about 1/30 of that in human hemolysate.