Important for recycling the chief excitatory neurotransmitter, glutamate, during neurotransmission. H2O + L-glutamate + NAD(+) = 2-oxoglutarate + H(+) + NADH + NH4(+) H2O + L-glutamate + NADP(+) = 2-oxoglutarate + H(+) + NADPH + NH4(+) Homohexamer. Expressed in retina, testis and, at a lower level, brain. Stoichiometry shows that ADP-ribosylation occurs in one subunit per catalytically active homohexamer. Belongs to the Glu/Leu/Phe/Val dehydrogenases family.