Reaction: 2 L-glutamate + NADP+ = L-glutamine + 2-oxoglutarate + NADPH + H+ (overall reaction)
(1a) L-glutamate + NH3 = L-glutamine + H2O
(1b) L-glutamate + NADP+ + H2O = NH3 + 2-oxoglutarate + NADPH + H+
For diagram of reaction click here.
Other name(s): glutamate (reduced nicotinamide adenine dinucleotide phosphate) synthase; L-glutamate synthase; L-glutamate synthetase; glutamate synthetase (NADP); NADPH-dependent glutamate synthase; glutamine-ketoglutaric aminotransferase; NADPH-glutamate synthase; NADPH-linked glutamate synthase; glutamine amide-2-oxoglutarate aminotransferase (oxidoreductase, NADP); L-glutamine:2-oxoglutarate aminotransferase, NADPH oxidizing; GOGAT
Systematic name: L-glutamate:NADP+ oxidoreductase (transaminating)
Comments: Binds FMN, FAD, 2 [4Fe-4S] clusters and 1 [3Fe-4S] cluster. The reaction takes place in the direction of L-glutamate production. The protein is composed of two subunits, α and β. The α subunit is composed of two domains, one hydrolysing L-glutamine to NH3 and L-glutamate (cf. EC 3.5.1.2, glutaminase), the other combining the produced NH3 with 2-oxoglutarate to produce a second molecule of L-glutamate (cf. EC 1.4.1.4, glutamate dehydrogenase [NADP+]). The β subunit transfers electrons from the cosubstrate The NH3 is channeled through a 31 Å channel in the active protein. In the absence of the β subunit, coupling between the two domains of the α subunit is compromised and some ammonium can be produced. In the intact alphaβ complex, ammonia production only takes place as part of the overall reaction.
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 37213-53-9
References:
1. Miller, R.E. and Stadtman, E.R. Glutamate synthase from Escherichia coli. An iron-sulfide flavoprotein. J. Biol. Chem. 247 (1972) 7407-7419. [PMID: 4565085]
2. Tempest, D.W., Meers, J.L. and Brown, C.M. Synthesis of glutamate in Aerobacter aerogenes by a hitherto unknown route. Biochem. J. 117 (1970) 405-407. [PMID: 5420057]
3. Vanoni, M.A. and Curti, B. Glutamate synthase: a complex iron-sulfur flavoprotein. Cell. Mol. Life Sci. 55 (1999) 617-638. [PMID: 10357231]
4. Ravasio, S., Curti, B. and Vanoni, M.A. Determination of the midpoint potential of the FAD and FMN flavin cofactors and of the 3Fe-4S cluster of glutamate synthase. Biochemistry 40 (2001) 5533-5541. [PMID: 11331018]