Which of the following represents the primary function of the pentose phosphate pathway in erythrocytes?
Erythrocytes are the specialized oxygen transpoing cells of the body. As such, they are continuously exposed to an oxidizing environment. These conditions can have profound effects on membrane lipids as a consequence of their attack by peroxides (paicularly hydrogen peroxide) prevalent in this environment. During the reduction of hydrogen peroxide catalyzed by glutathione peroxidase, glutathione acts as a donor of the necessary reducing equivalent generating oxidized glutathione. Glutathione (GSH) is a tripeptide of the structure gamma glutamyl cysteinyl-glycine, where the cysteine sulfhydryl side chains can form a disulfide bond between two molecules (designated as GSSG). To again perform the role of cofactor for glutathione peroxidase, the disulfide bond of GSSG must be reduced. This reaction is catalyzed by glutathione reductase which requires NADPH as a cofactor. Therefore, in order to maintain a red cell membrane structure, erythrocytes utilize the pentose phosphate pathway for the generation of large amounts of NADPH. Erythrocytes are enucleate and therefore do not synthesize DNA and have no need for ribose-5-phosphate. Production of 2, 3- diphosphoglycerate occurs through a side reaction of glycolysis, not the pentose phosphate pathway. The pentose phosphate pathway does not generate ATP or result in the reduction of hydrogen peroxide. Ref: Bender D.A., Mayes P.A. (2011). Chapter 21. The Pentose Phosphate Pathway & Other Pathways of Hexose Metabolism. In D.A. Bender, K.M. Botham, P.A. Weil, P.J. Kennelly, R.K. Murray, V.W. Rodwell (Eds), Harper's Illustrated Biochemistry, 29e.
Production of NADPH
Production of Ribose-5-phosphate
Remodeling of dietary carbon atoms into two, three-bisphosphoglycerate
Synthesis of ATP