Catalyzes the incorporation of an ammonium ion into alpha-ketoglutarate to form L-glutamate, the major route of assimilation of ammonia into an organic form in yeast. H2O + L-glutamate + NADP(+) = 2-oxoglutarate + H(+) + NADPH + NH4(+) Homohexamer. Present with 77500 molecules/cell in log phase SD medium. Belongs to the Glu/Leu/Phe/Val dehydrogenases family.