The Role of Nonhemoglobin Proteins and Reduced Glutathione in the Protection of Hemoglobin from Oxidation In Vitro*

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Abstract
The oxidation of hemoglobin to sulf-hemoblobin was accelerated in the presence of ascorbic acid. This augmentation was of small measure when fresh erythrocytes were used, of moderate degree in fresh whole hemolysates, and of greatest magnitude in hemoglobin solutions free of most erythrocytic enzymes. In the first instance inhibition of catalase enhanced the oxidative change. Reduced glutathione had little protective effect on the oxidation of human hemoglobin in the presence of ascorbic acid or acetylphenylhydrazine unless a hear labile nondialyzable, erythrocytic, nonhemoglobin protein factor was present. The existence of a glutathione peroxidase activity in human erythrocytes has been demonstrated. In the presence of oxidizing agents, in vitro, glutathione peroxidase may mediate the preferential oxidation of glutathione rather than of hemoglobin, as might otherwise occur.