Category: catabolism
Cytosolic alternative glucose oxidation generating NADPH (reducing power for biosynthesis + glutathione regeneration) + ribose-5-phosphate (nucleotide precursor). Oxidative branch (irreversible): G6P → 6-phosphogluconolactone → 6-phosphogluconate → ribulose-5-P, producing 2 NADPH per G6P. Non-oxidative branch (reversible): ribulose-5-P interconverts with ribose-5-P, sedoheptulose-7-P, fructose-6-P, glyceraldehyde-3-P — balances supply between nucleotide and glycolytic demands. G6PD is rate-limiting + X-linked; deficiency is the most common human enzymopathy (~400M carriers) and produces hemolytic anemia on oxidative stress (primaquine, sulfa, fava beans, dapsone, methylene blue).