Involved in glutamate biosynthesis. Required for non-photorespiratory ammonium assimilation. Probably involved in primary ammonium assimilation in roots. 2 L-glutamate + NAD(+) = 2-oxoglutarate + H(+) + L-glutamine + NADH Binds 1 [3Fe-4S] cluster. Amino-acid biosynthesis; L-glutamate biosynthesis via GLT pathway; L-glutamate from 2-oxoglutarate and L-glutamine (NAD(+) route): step 1/1. Energy metabolism; nitrogen metabolism. Monomer. Highly expressed in roots and at low levels in leaves. Induced by cadmium. Defect in growth and glutamate biosynthesis under non-photorespiratory conditions. Belongs to the glutamate synthase family.