[Purification and characterization of glutamine synthetase from chicken brain]

A procedure for the isolation and purification to homogeneity of glutamine synthetase (E.C. 6.3.1.2.) from chick brain is described. The physico-chemical properties of the purified enzyme preparation are similar to those of other eucaryotic glutamine synthetases. The optimum activity of glutamine synthetase is dependent on the Mg++ to ATP ratio in the reaction mixture rather than on the magnesium or ATP concentrations. The characteristics of the enzyme studied through various phylogenetic trees suggest that this enzyme is preserved during evolution.