D-glyceraldehyde 3-phosphate + NAD(+) + phosphate = (2R)-3-phospho-glyceroyl phosphate + H(+) + NADH Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 1/5. Homotetramer. Plants contain three forms of GAPDH: a cytosolic form which participates in glycolysis and two chloroplast forms which participates in photosynthesis. These three forms are encoded by distinct genes. Belongs to the glyceraldehyde-3-phosphate dehydrogenase family.