Enzymatic Inactivation of Glutamine Synthetase in Enterobacteriaceae

The inactivation of glutamine synthetase in vivo on addition of ammonium ions to the culture medium was studied in different microorganisms. Only those belonging to the family of Enterobacterioceae showed inactivation. The transfer activity of the enzyme was much less affected than the synthetic one. As in Escherichia coli, the glutamine synthetase of Salmonella typhimurium could be inactivated in vitro in a system requiring glutamine, ATP, Mg2+ and an enzyme.The inactivating enzymes of E. coli and S. typhimurium have been separated and cross‐tested against their synthetases. The inactivating enzymes inactivated both glutamine synthetases in the in vitro inactivation process. In contrast, synthetases of microorganisms which did not exhibit in vivo inactivation were not affected by these inactivating enzymes.The fact that only glutamine synthetases of Enterobacteriaceae could be inactivated suggests that this regulatory mechanism is limited to a group of organisms possibly derived from the same ancestor.