Glucose-6-phosphate dehydrogenase (G6PDor G6PDH) is a cytosolic enzyme that catalyzes the chemical reaction : D-glucose 6-phosphate + NADP+ ⇌ 6-phospho-D-glucono-1,5-lactone + NADPH + H+ The NADPH in turn maintains the level of glutathione in these cells that helps protect the red blood cells against oxidative damage from compounds like hydrogen peroxide. Clinically, an X-linked genetic deficiency of G6PD predisposes a person to non-immune hemolytic anemia.