Editing Glutamine (section)

===Biosynthesis===
Glutamine synthesis from [[glutamate]] and ammonia is catalyzed by the [[enzyme]] [[glutamine synthetase]]. The majority of glutamine production occurs in muscle tissue, accounting for about 90% of all glutamine synthesized. Glutamine is also released, in small amounts, by the lungs and brain.<ref>{{cite journal | vauthors = Newsholme P, Lima MM, Procopio J, Pithon-Curi TC, Doi SQ, Bazotte RB, Curi R | title = Glutamine and glutamate as vital metabolites | journal = Brazilian Journal of Medical and Biological Research = Revista Brasileira de Pesquisas Medicas e Biologicas | volume = 36 | issue = 2 | pages = 153–163 | date = February 2003 | pmid = 12563517 | doi = 10.1590/S0100-879X2003000200002 | doi-access = free }}</ref> Although the liver is capable of  glutamine synthesis, its role in glutamine metabolism is more regulatory than productive, as the liver takes up glutamine derived from the gut via the [[hepatic portal system]].<ref name="Brosnan"/>