Glucose-6-Phosphate Dehydrogenase in Mature Erythrocytes

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Abstract
The red blood cell has a limited metabolism, deriving its energy from the utilization of glucose via the Embden-Meyerhof pathway (which generates ATP and NADH) or the pentose phosphate pathway which generates NADPH. In considering the role of glucose -6 -phosphate (G-6-P) dehydrogenase in mature circulating erythrocytes, it is seen that this enzyme catalyzes the 1st of the 2 oxidative reactions of the pentose phosphate pathway which are major sites of NADPH generation in these cells. The importance of the various metabolic functions of NADPH to the viability of the human red cell in vivo is largely determined by the specific environmental conditions of the cell. In studies with hemolysates and with intact red cells in vitro, marked alterations in the rate of G-6-P oxidation via the G-6-P dehydrogenase reaction could be induced by various agents, including such physiologic substances as pyruvate, ascorbic acid, and cysteine. A consideration of the role of G-6-P dehydrogenase in determining the life span of the circulating red cell has relevance only in the context of the in vivo conditions of the cells.