Glyceraldehyde-3-phosphate dehydrogenase (NADP+) () (GAPN) is an enzyme that irreversibly catalyzes the oxidation of glyceraldehyde-3-phosphate (GAP) to 3-phosphoglycerate (3-PG or 3-PGA) using the reduction of NADP+ to NADPH. GAPN is used in a variant of glycolysis that conserves energy as NADPH rather than as ATP. The NADPH and 3-PG can then be used for synthesis. The most familiar variant of glycolysis uses glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and phosphoglycerate kinase to produce ATP. GAPDH is phosphorylating. GAPN is non-phosphorylating.
GAPN was reported first by Rosenberg and Arnon in 1954. It has been found in plants, algae, and bacteria.
Glyceraldehyde-3-phosphate dehydrogenase (NADP+) catalyzes the reaction:
Glyceraldehyde-3-phosphate dehydrogenase takes the same substrate but converts it to 1,3-bisphosphoglyceric acid, adding a phosphate group (P<sub>i</sub>):