Biochemical and physiological aspects of glutamine synthetase inactivation in Saccharomyces cerevisiae.

Saccharomyces cerevisiae glutamine synthetase is inactivated in vivo by the addition of glutamine or ammonia. Inactivation is characterized by a specific loss of synthetase activity; transferase activity remains stable. Several physiological perturbations cause inactivation, such as carbon starvation or limitation for a required amino acid, which could cause a buildup of glutamine. The kinetics of reappearance of synthetase activity after inactivation suggest that the process is reversible in vivo. No change in the native size of the enzyme was associated with inactivation but there appears to be a change in the immunological properties of the enzyme subunit.