The amidotransferase family of enzymes utilises the ammonia derived from the hydrolysis of glutamine for a subsequent chemical reaction catalyzed by the same enzyme. The ammonia intermediate does not dissociate into solution during the chemical transformations [1].
GMP synthetase is a glutamine amidotransferase from the de novo purine biosynthetic pathway. The C-terminal domain is specific to the GMP synthases EC:6.3.5.2. In prokaryotes this domain mediates dimerisation. Eukaryotic GMP synthases are monomers. This domain in eukaryotes includes several large insertions that may form globular domains [2].
Raushel FM, Thoden JB, Holden HM.
The amidotransferase family of enzymes: molecular machines for the production and delivery of ammonia.
Biochemistry 38 7891-9 1999
[PubMed: 10387030] http://dx.doi.org/10.1021/bi990871p
2.
Tesmer JJ, Klem TJ, Deras ML, Davisson VJ, Smith JL.
The crystal structure of GMP synthetase reveals a novel catalytic triad and is a structural paradigm for two enzyme families.
Nat. Struct. Biol. 3 74-86 1996
[PubMed: 8548458] http://dx.doi.org/10.1038/nsb0196-74