Catalase like action

Hemocyanin possesses a catalase-like action (10, 12), albeit a weak one, in that it decomposes hydrogen peroxide into water and oxygen just as the hemeprotein catalase. The catalase-like action of hemocyanin is due to the protein-bound copper since neither copper-free hemocyanin nor free copper ions exhibit activity under equivalent conditions. Copper-amino acid complexes have been tested for catalase-like action, and it was reported that only the copper-arginine complex possesses catalase-like activity (13). However, we have found (37) as have other investigators (29, 40), that other amino acid complexes of copper also decompose H202. 

The catalase-like action of hemocyanin is probably because of copper bound to one or more amino acids in the protein. Contrary to previous claims (12), arginine chelates with copper are not the only catalytically active species. For example, copper chelates with histidine and histamine are also active. The rates appear to be a first power function of copper and H202. Studies now being carried out with V. S. Sharma in our laboratories indicate that the active species is the Cu (II) L form where L represents the ligand. The copper chelate forms a ternary complex with... 

Hemocyanin from molluscan and crustacean sources is able to decompose hydrogen peroxide catalytically (Ghiretti, 1956 Felsenfeld and Printz, 1959). This catalase-like action is due to the presence of copper in the hemocyanin molecule. However, equivalent amounts of copper alone have no effect on the decomposition of HgOj. Among the copper complexes of the amino acid tested, only Cu-arginine is active. 

Other effects of ascorbic acid are probably also dependent upon the monodehydroascorbic free radical. One is the depolymerization of hyaluronic acid, first shown by Robertson et al. (R14). This is particularly likely, since subsequent studies have shown that the depolymerization was not prevented by catalase, as should have occurred if peroxide were the active component. There is no reason to believe that this hyaluroni-dase-like action is physiological. There is every reason to believe, however, that the monodehydroascorbic acid radical is formed in vivo. It is unlikely that all of the reactions in the body of such a reactive molecule are catalyzed by enzymes. 

Nifurtimox (Lampit) is a nitrofuran derivative whose likely mechanism of action for kUhng of trypanosomes is through the production of activated forms of oxygen. Nifurtimox is reduced to the nitro anion radical, which reacts with oxygen to produce superoxide and hydrogen peroxide. The free radical metabolites, an absence of parasite catalase, and a peroxide dehciency lead to hpid peroxidation and cell damage. This production of activated oxygen results in toxicity to the protozoal cells. 

Galactose oxidase of P. circinatus was apparently inhibited by traces of BESOD. It can be inactivated by H Oj produced in the reaction unless catalase was added. There was an activation by traces of O J. In the absence of oxidants the reaction usually showed an induction period The enzyme, used at very low concentrations in the assays, was protected by proteins like serumalbumin. SOD did, however, not alter the reaction rate when added after 15 min This was interpreted by an inactivation of SOD by the H O accumulated in the reaction but it could just as well mean that SOD had no effect on the active enzyme, but that it did lower the activation in the induction period. Peroxidase activated galactose oxidase and suppressed the effect of SOD It did protect the enzyme against H O inactivation and could have been responsible for appreciable amounts of OJ, produced from O and from radicals formed in its action on a substrate. 

---