Hemoglobin catabolism. II. The protection of hemoglobin from oxidative breakdown in the intact erythrocyte.

This protective system has a lasting effect only when the product of the reaction, GSSG, is continuously reduced to GSH. The work of previous investigators has shown that erythrocytes have an effective system for reducing GSSG (5-8). The TPN-linked reactions of the phosphogluconate pathway, in conjunction with glutathione reductase, maintain erythrocyte glutathione in the reduced state. In the present studies, catalase and the peroxidase-GSH system of intact erythrocytes are shown to protect hemoglobin from oxidative breakdown brought about in the presence of ascorbic acid. When glucose is absent from the incubation medium, the protective effect of the peroxidase-GSH system is lost. This failure is due to the inability of the cell to reduce GSSG. The result is a rapid drop in the GSH level and subsequent loss of the protective effect of the peroxidase-GSH system. The protective effect of catalase in intact erythrocytes is eliminated by azide, a fact which has been demonstrated previously by Foulkes and Lemberg (1). In addition, studies with hemolysates show that the peroxidase-GSH protective system is effective in the presence of either glucose 6-phosphate, 6-phosphogluconate, or ribose 5-phosphate. These three compounds have been found previously to be effective in reducing GSSG to GSH in erythro-