Forms L-glutamate from L-glutamine and 2-oxoglutarate. Represents an alternative pathway to L-glutamate dehydrogenase for the biosynthesis of L-glutamate (PubMed:7773104). Participates with glutamine synthetase in ammonia assimilation processes (PubMed:7773104). The enzyme is specific for NADH, L-glutamine and 2-oxoglutarate (PubMed:7773104). 2 L-glutamate + NAD(+) = 2-oxoglutarate + H(+) + L-glutamine + NADH Binds 1 [3Fe-4S] cluster. In the presence of 10 mM allantoin, the activity is reduced more than 25%. Optimum pH is 6.35. Optimum temperature is 40 degrees Celsius. 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. Homotrimer. Belongs to the glutamate synthase family.