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The Pentose Phosphate Pathway and Hemolytic Anemia
The pentose phosphate pathway is the only source of NADPH in red blood cells, which, as a result, are highly dependent on the proper functioning of the enzymes involved. A glucose-6-phosphate dehydrogenase deficiency leads to an NADPH deficiency, which can, in turn, lead to hemolytic anemia because of wholesale destruction of red blood cells.
The relationship between NADPH deficiency and anemia is an indirect one. NADPH is required to reduce the peptide gluta-thione from the disulfide to the free thiol form. Mammalian red blood cells lack mitochondria, which host many redox reactions.
Consequently, these cells are limited in the ways in which they can deal with redox balance. A substance like glutathione, which can take part in redox reactions, assumes greater importance than would be the case in cells with large numbers of mitochon-dria.
The presence of the reduced form of glutathione is neces-sary for the maintenance of the sulfhydryl groups of hemoglobin and other proteins in their reduced forms, as well as for keeping the Fe(II) of hemoglobin in its reduced form.
Glutathione also maintains the integrity of red cells by react-ing with peroxides that would otherwise degrade fatty-acid side chains in the cell membrane. About 11% of African-Americans are affected by glucose-6-phosphate dehydrogenase deficiency.
This condition, like the sickle-cell trait, leads to increased resistance to malaria, accounting for some of its persistence in the gene pool in spite of its otherwise deleterious consequences.
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