G6PD and G6PD deficiency: Observations of primaquine-induced hemolysis led ultimately to the identification of inherited glucose-6-phosphate dehydrogenase (G6PD) deficiency.5 G6PD catalyzes the first step in the pentose phosphate pathway, protecting against oxidative stress by generating reduced nicotinamide adenine dinucleotide phosphate (NADPH) for reduction cycling of glutathione.