D-glyceraldehyde 3-phosphate + NADP(+) + phosphate = (2R)-3-phospho-glyceroyl phosphate + H(+) + NADPH Carbohydrate biosynthesis; Calvin cycle. Homotetramer. Repressed by addition of D-galactose, D-mannose, D-glucose, D-ribose or sucrose, but not by the addition of non-metabolizable sugar analogs. 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.