In enzymology, a glutamate synthase (NADH) (EC 1.4.1.14) is an enzyme that catalyzes the chemical reaction

2 L-glutamate + NAD⁺ ${\displaystyle \rightleftharpoons }$ L-glutamine + 2-oxoglutarate + NADH + H⁺

Glutamate synthase facilitates the ammonium assimilation pathway, which follows the enzymes, nitrite reductase and glutamine synthase.^[1] An ammonium produced by the nitrite reductase reaction will be incorporated into carbon skeleton backbone by glutamine synthase.^[2] Glutamine will be produced because of the introduction of ammonium in the carbon backbone, which can be converted into glutamate by glutamate synthase of another pathway.^[2]

These processes are common in plant roots because if the nitrogen deficient conditions exist (with access to ammonium and nitrate ions), there will be a first priority of ammonium uptake.^[1] Thus, the two substrates of this enzyme are L-glutamate and NAD⁺, whereas its 4 products are L-glutamine, 2-oxoglutarate, NADH, and H⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH₂ group of donors with NAD⁺ or NADP⁺ as acceptor. This enzyme participates in glutamate metabolism and nitrogen assimilation. It employs one cofactor, FMN.

The systematic name of this enzyme class is L-glutamate:NAD⁺ oxidoreductase (transaminating). Other names in common use include:

• glutamate (reduced nicotinamide adenine dinucleotide) synthase,
• glutamate synthase (NADH),
• L-glutamate synthetase(NADH),
• NADH-dependent glutamate synthase,
• NADH-glutamate synthase, and
• NADH-Glutamine oxoglutarate aminotransferase (NADH-GOGAT).

• Glutamate synthase (ferredoxin)
• Glutamate synthase (NADPH)

• Boland MJ, Benny AG (1977). "Enzymes of nitrogen metabolism in legume nodules. Purification and properties of NADH-dependent glutamate synthase from lupin nodules". Eur. J. Biochem. 79 (2): 355–62. doi:10.1111/j.1432-1033.1977.tb11816.x. PMID 21790.