D-glyceraldehyde 3-phosphate + NADP(+) + phosphate = (2R)-3-phospho-glyceroyl phosphate + H(+) + NADPH Carbohydrate biosynthesis; Calvin cycle. Homotetramer. Component of a complex that contains two dimers of PRK, two tetramers of GAPDH and CP12. CP12 associates with GAPDH, causing its conformation to change. This GAPDH/CP12 complex binds PRK to form a half-complex (one unit). This unit probably dimerizes due partially to interactions between the enzymes of each unit. GAPDHB, the second subunit found in plants, is absent in algae. Algae contain three forms of GAPDH: two cytosolic forms which participate in glycolysis and one chloroplastic form which participates in photosynthesis. These three forms are encoded by distinct genes. Belongs to the glyceraldehyde-3-phosphate dehydrogenase family.