This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: GS/GOGAT pathway
|Superclasses:||Degradation/Utilization/Assimilation → Inorganic Nutrients Metabolism → Nitrogen Compounds Metabolism → Ammonia Assimilation|
Expected Taxonomic Range: Viridiplantae
The primary nitrogen assimilation routes in photosynthetic eukaryotes and prokaryotes are nitrogen fixation, nitrate assimilation, and ammonia assimilation. Ammonia is liberated by photorespiration, protein and amino acid metabolism, and the breakdown of nitrogen transport compounds. The rate of ammonia generation during photorespiration is about 10 times the rate of nitrate assimilation.
The ammonia released from photorespiration is immediately re-assimilated via the ammonia assimilation cycle. The net result of this cycle is the conversion of one molecule of ammonia to one molecule of glutamate at the expense of one ATP molecule.
The pathway includes two steps catalyzed by glutamine synthetase (GS) and glutamate synthase (also known as glutamine oxoglutarate aminotansferase or GOGAT), and thus is often referred to as the GS/GOGAT pathway. Two types of GOGAT are known in photosynthetic organisms - NADH-dependent, and ferredoxin-dependent. NADH-GOGAT is found in the nucleus of vascular plants, fungi, and diatoms. The ferredoxin-dependent enzyme is only found in Cyanobacteria and photosynthetic eukaryotes. Plants possess both enzymes.
An NADPH-dependent version of GOGAT is found in non-photosynthetic bacteria and archaea (see ammonia assimilation cycle III).
Variants: ammonia assimilation cycle III
Unification Links: AraCyc:PWY-3282
Miflin02: Miflin BJ, Habash DZ (2002). "The role of glutamine synthetase and glutamate dehydrogenase in nitrogen assimilation and possibilities for improvement in the nitrogen utilization of crops." J Exp Bot 53(370);979-87. PMID: 11912240
Alibhai94: Alibhai M, Villafranca JJ (1994). "Kinetic and mutagenic studies of the role of the active site residues Asp-50 and Glu-327 of Escherichia coli glutamine synthetase." Biochemistry 33(3);682-6. PMID: 7904829
Amaya05: Amaya KR, Kocherginskaya SA, Mackie RI, Cann IK (2005). "Biochemical and mutational analysis of glutamine synthetase type III from the rumen anaerobe Ruminococcus albus 8." J Bacteriol 187(21);7481-91. PMID: 16237031
Balakrishnan78: Balakrishnan MS, Villafranca JJ (1978). "Distance determinations between the metal ion sites of Escherichia coli glutamine synthetase by electron paramagnetic resonance using Cr(III)--nucleotides as paramagnetic substrate analogues." Biochemistry 17(17);3531-8. PMID: 28753
Bender77: Bender RA, Janssen KA, Resnick AD, Blumenberg M, Foor F, Magasanik B (1977). "Biochemical parameters of glutamine synthetase from Klebsiella aerogenes." J Bacteriol 129(2);1001-9. PMID: 14104
Boland77: 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. PMID: 21790
Cogoni95: Cogoni C, Valenzuela L, Gonzalez-Halphen D, Olivera H, Macino G, Ballario P, Gonzalez A (1995). "Saccharomyces cerevisiae has a single glutamate synthase gene coding for a plant-like high-molecular-weight polypeptide." J Bacteriol 177(3);792-8. PMID: 7836314
CohenKupiec93: Cohen-Kupiec R, Gurevitz M, Zilberstein A (1993). "Expression of glnA in the cyanobacterium Synechococcus sp. strain PCC 7942 is initiated from a single nif-like promoter under various nitrogen conditions." J Bacteriol 175(23);7727-31. PMID: 7902350
Coschigano98: Coschigano KT, Melo-Oliveira R, Lim J, Coruzzi GM (1998). "Arabidopsis gls mutants and distinct Fd-GOGAT genes. Implications for photorespiration and primary nitrogen assimilation." Plant Cell 10(5);741-52. PMID: 9596633
Dahlquist75: Dahlquist FW, Purich DL (1975). "Regulation of Escherichia coli glutamine synthetase. Evidence for the action of some feedback modifiers at the active site of the unadenylylated enzyme." Biochemistry 14(9);1980-9. PMID: 235974
Dhalla94: Dhalla AM, Li B, Alibhai MF, Yost KJ, Hemmingsen JM, Atkins WM, Schineller J, Villafranca JJ (1994). "Regeneration of catalytic activity of glutamine synthetase mutants by chemical activation: exploration of the role of arginines 339 and 359 in activity." Protein Sci 3(3);476-81. PMID: 7912599
Esposito05: Esposito S, Guerriero G, Vona V, Di Martino Rigano V, Carfagna S, Rigano C (2005). "Glutamate synthase activities and protein changes in relation to nitrogen nutrition in barley: the dependence on different plastidic glucose-6P dehydrogenase isoforms." J Exp Bot 56(409);55-64. PMID: 15501908
Gregerson93: Gregerson RG, Miller SS, Twary SN, Gantt JS, Vance CP (1993). "Molecular characterization of NADH-dependent glutamate synthase from alfalfa nodules." Plant Cell 5(2);215-26. PMID: 8453303
Hayakawa93: Hayakawa T, Yamaya T, Mae T, Ojima K (1993). "Changes in the Content of Two Glutamate Synthase Proteins in Spikelets of Rice (Oryza sativa) Plants during Ripening." Plant Physiol 101(4);1257-1262. PMID: 12231780
Hofmann78: Hofmann GE, Glaunsinger WS (1978). "EPR investigation of the Mn(II) binding sites in glutamine synthetase (Escherichia coli W). I. High-affinity binding sites." J Biochem (Tokyo) 83(6);1769-78. PMID: 27502
Hofmann78a: Hofmann GE, Glaunsinger WS (1978). "EPR investigation of the Mn(II) binding sites in glutamine synthetase (Escherichia coli W). II. Intermediate-affinity binding sites." J Biochem (Tokyo) 83(6);1779-82. PMID: 27503
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