Catalyzes the reversible oxidative deamination of L-glutamate to 2-oxoglutarate and ammonia, thereby playing a key role at the intersection of the carbon and nitrogen metabolic pathways. Shows a high preference for NADP(+)/NADPH as the acceptor/donor over NAD(+)/NADH. May function in vivo in the synthetic direction. Also catalyzes at very low rates the oxidative deamination of L-2-aminobutyrate, and the reductive amination of 2-oxovalerate and 2-oxobutyrate. H2O + L-glutamate + NADP(+) = 2-oxoglutarate + H(+) + NADPH + NH4(+) Is not regulated allosterically. Activity is inhibited in the presence of high ionic strength; the inhibitory effect of KCl is slightly higher than that of NaCl. kcat is 13 sec(-1) for oxidative deamination of L-glutamate, and 95 sec(-1) for reductive amination of 2-oxoglutarate (at 50 degrees Celsius). Optimum pH is 9.5 for oxidative deamination, and 9.0 for reductive amination. Retains more than 80% of its activity after incubation for 30 minutes at pH 4.5-9.5. Optimum temperature is 90 degrees Celsius for oxidative deamination. Retains full activity after incubation for 10 minutes at temperatures up to 90 degrees Celsius. Homohexamer. Is constitutively expressed. Belongs to the Glu/Leu/Phe/Val dehydrogenases family.