If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: glutamine - glutamate pathway
|Superclasses:||Biosynthesis → Amino Acids Biosynthesis → Individual Amino Acids Biosynthesis → Glutamine Biosynthesis|
Pathway Summary from MetaCyc:
The amino acid glutamine is a constituent of proteins and a nitrogen donor for many biosynthetic reactions, including the biosynthesis of amino acids, purines, pyrimidines, glucosamime and carbamoyl phosphate. The biosynthesis of glutamine is catalyzed by glutamine synthetase, a key enzyme of nitrogen metabolism found in all domains of life. Phylogenetic analysis of glutamine synthetase genes has suggested that they are among the oldest functioning genes in the history of evolution [Kumada93]. In microorganisms and plants, glutamine synthetase (also known as GS) has a role in ammonia assimilation in combination with glutamate synthase (glutamine: α-oxoglutarate aminotransferase, or GOGAT) as indicated by the pathway links and pathways ammonia assimilation cycle III and superpathway of ammonia assimilation (plants)). This is known as the GS/GOGAT pathway [Gottschalk86].
About this pathway
There are three types of glutamine synthetase, differing in number of subunits. Glutamine synthetase type I is found mostly in bacteria and archaea, including Escherichia coli K-12 and Salmonella enterica enterica serovar Typhimurium (reviewed in [Stadtman01]). It is a well-studied homododecamer built from two back-to-back hexameric rings. Glutamine synthetase type II is found mostly in eukaryotes and some soil bacteria, but it has also been described in the halophilic archaeon Haloferax mediterranei [MartinezEspinos06]. It is a homooctamer. Type III glutamine synthetase has been described in anaerobic bacteria (such as Ruminococcus albus 8) and cyanobacteria, and is generally a homohexamer. The active site residues of all three types of glutamine synthetase are conserved. In [MartinezEspinos06, Amaya05, Llorca06].
Superpathways: ammonia assimilation cycle III
Pathway Evidence Glyph:
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
Kumada93: Kumada Y, Benson DR, Hillemann D, Hosted TJ, Rochefort DA, Thompson CJ, Wohlleben W, Tateno Y (1993). "Evolution of the glutamine synthetase gene, one of the oldest existing and functioning genes." Proc Natl Acad Sci U S A 90(7);3009-13. PMID: 8096645
Llorca06: Llorca O, Betti M, Gonzalez JM, Valencia A, Marquez AJ, Valpuesta JM (2006). "The three-dimensional structure of an eukaryotic glutamine synthetase: functional implications of its oligomeric structure." J Struct Biol 156(3);469-79. PMID: 16884924
MartinezEspinos06: Martinez-Espinosa RM, Esclapez J, Bautista V, Bonete MJ (2006). "An octameric prokaryotic glutamine synthetase from the haloarchaeon Haloferax mediterranei." FEMS Microbiol Lett 264(1);110-6. PMID: 17020556
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