Tissue distribution of monomeric glutathione peroxidase in broiler chicks

It is known that there are two kinds of enzymes which show glutathione peroxidase activity, 'classical' glutathione peroxidase and glutathione S-transferase. Recently, a third enzyme was found, monomeric glutathione peroxidase, in broiler chick liver cytosolic fraction. To gain an insight into the possible physiological role of the monomeric glutathione peroxidase, the distribution of this enzyme in other broiler tissues was studied. The monomeric glutathione peroxidase was found in all tissues examined and in erythrocytes. The percentage of the total glutathione peroxidase activity accounted for by the monomeric enzyme ranged from 4 per cent in erythrocytes to 28 per cent in liver. Livers from three avian and two mammalian species contained the monomeric glutathione peroxidase. The contribution of the monomeric enzyme to total glutathione peroxidase activity with cumene hydroperoxide was high in poultry livers, while only trace monomeric glutathione peroxidase activity was found in mammalian livers. Chick monomeric glutathione peroxidase showed high activity toward phospholipid hydroperoxide. Thus, monomeric glutathione peroxidase might be an important enzyme in reducing membrane lipid hydroperoxides in birds.