Key enzyme in glycolysis that catalyzes the first step of the pathway by converting D-glyceraldehyde 3-phosphate (G3P) into 3-phospho-D-glyceroyl phosphate. Essential for the maintenance of cellular ATP levels and carbohydrate metabolism (By similarity). Binds DNA in vitro (PubMed:22589465). Together with DNA polymerase II subunit B3-1 (DPB3-1) and GAPC1, enhances heat tolerance and promotes the expression of heat-inducible genes (PubMed:32651385). D-glyceraldehyde 3-phosphate + NAD(+) + phosphate = (2R)-3-phospho-glyceroyl phosphate + H(+) + NADH Inhibition by oxidized glutathione (GSSG), S-nitrosoglutathione (GSNO) and hydrogen peroxide. Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 1/5. Homotetramer (By similarity). Interacts with PLDDELTA (By similarity). Binds to DPB3-1/NF-YC10 in response to heat-stress; this interaction promotes DPB3-1/NF-YC10 DNA-binding ability to its target promoter (PubMed:32651385). Accumulates in the nucleus under heat stress. A number of isoforms are produced. According to EST sequences. S-glutathionylation at Cys-156 in the presence of oxidized glutathione (GSSG). S-nitrosylation at Cys-156 and Cys-160 in the presence of S-nitrosoglutathione (GSNO) or sodium nitroprusside (SNP). These reactions may be both a protective mechanism against irreversible oxidation and a mean to store inhibited enzyme in a recoverable form. The double mutant gapc1 gapc2 has an impaired ability to enhance heat tolerance of seedlings and to promote the expression of heat-inducible genes. Plants contain three types of GAPDH: NAD-dependent cytosolic forms which participate in glycolysis, NAD-dependent chloroplastic forms which participate in plastidic glycolysis and NADP-dependent chloroplastic forms which participate in the photosynthetic reductive pentose phosphate pathway (Calvin-Benson cycle). All the forms are encoded by distinct genes. Belongs to the glyceraldehyde-3-phosphate dehydrogenase family.