Studies on Rat Liver Glutamine Synthetase

Rat liver glutamine synthetase is activated by Mg ++ and by Mn ++ . Optimal activity of the Mg ++ activated synthetase occurred at about pH 7.8. The pH optimum of the Mn ++ activated enzyme varied from 6.2 at low Mn ++ concentrations to 4.4 at high Mn ++ concentrations. α‐N‐Ethyl‐L‐glutamine inhibits the synthetase activity. The inhibition is of a mixed type. The synthetase is also inhibited, to a lesser degree, by α‐N‐propyl‐L‐glutamine but not by α‐N‐butyl‐L‐glutamine.