Catalyzes the irreversible NAD(P)-dependent non-phosphorylating oxidation of glyceraldehyde-3-phosphate (GAP) to 3-phosphoglycerate (3PG). It is highly specific for D-GAP. D-glyceraldehyde 3-phosphate + H2O + NADP(+) = (2R)-3-phosphoglycerate + 2 H(+) + NADPH D-glyceraldehyde 3-phosphate + H2O + NAD(+) = (2R)-3-phosphoglycerate + 2 H(+) + NADH Allosterically activated by AMP, ADP, glucose 1-phosphate (G1P), and fructose 6-phosphate (F6P). Km applies to a data set exhibiting Michaelis-Menten kinetics. When an enzyme does not exhibit Michaelis-Menten kinetics the binding affinity is simply expressed as S0.5 which corresponds to the observed substrate concentration for 0.5 x Vmax. S0.5 is 20 mM for NADP alone, 0.1 mM for NADP with G1P as effector, 0.2 mM for NADP with F6P as effector, 0.15 mM for NADP with AMP as effector and 0.2 mM for NADP with ADP as effector. Optimum temperature is 96 degrees Celsius. High thermostability. Homotetramer. Dimer of dimers. GapN is also able to utilize NADP as a cosubstrate but with remarkably different kinetic properties. In contrast to the NAD-dependent reaction, the NADP-dependent reaction does not follow classical Michaelis-Menten kinetics. The saturation kinetics of the NADP-dependent reaction shows an unexpectedly bumpy curve with several more or less pronounced intermediate plateaus, which can be explained by the assumption that the catalytic or binding constants first decrease, then increase with saturation. The first saturation phase is characterized by negative cooperativity. The later saturation phases display sigmoidal shapes indicating positive cooperativity. The negative cooperativity of the first saturation phase could also explain the strong inhibition of NADP on the NAD-dependent reaction if it is assumed that NADP excludes NAD more efficiently from the vacant cosubstrate-binding site than NADP itself (PubMed:15288789). Belongs to the aldehyde dehydrogenase family.