Glutamine synthetase (<db_xref db="EC" dbkey="6.3.1.2"/>) (GS) [<cite idref="PUB00006495"/>] plays an essential role in the metabolism of nitrogen by catalyzing the condensation of glutamate and ammonia to form glutamine. Class I enzymes (GSI) are specific to prokaryotes, and are oligomers of 12 identical subunits. The activity of GSI-type enzyme is controlled by the adenylation of a tyrosine residue. The adenylated enzyme is inactive.<p>Recent reviews discuss: the discovery of the enzymatic synthesis of glutamine; the role of glutamine synthetase in defining the thermodynamics of ATPases; early isotopic tracer studies of the synthetase reaction; the proposed intermediacy of gamma-glutamyl-phosphate; the mechanism of methionine sulphoximine inhibition; stereochemical mapping of the enzyme's active site; detection of enzyme reaction cycle intermediates; borohydride trapping of gamma-glutamyl-P; positional isotope exchanges catalyzed by glutamine synthetase; regulation of bacterial enzyme; and how knowledge of the atomic structure of bacterial glutamine synthetase has clarified ligand binding interactions [<cite idref="PUB00006495"/>, <cite idref="PUB00006519"/>]. </p> Glutamine synthetase class-I, adenylation site