SUMMARY: The cloned glutamine synthetase (GS) subunit produced in had the same apparent of approximately 75000 as the GS subunit from cells. The GS enzyme had an apparent of approximately 490000 and it is concluded that the GS is a hexamer. The cloned GS did not appear to be regulated by adenylylation and deadenylylation and the cloned enzyme was inactivated by snake venom phosphodiesterase. The pH profiles of the cloned GS, assayed by the γ-glutamyl transferase (GGT) assay were similar for NH -shocked and unshocked cell extracts and an isoactivity point was not obtained from these curves. The cloned GS was subject to feedback inhibition by amino acids but not by AMP. The GGT activity of the cloned GS in NH -shocked and unshocked cell-free extracts was inhibited by Mg. Mn stimulated the cloned GS GGT activity of NH -shocked cell-free extracts. Western blotting indicated that GS production was regulated by nitrogen in cells but cell extracts showed no GGT activity. Cloned GS produced in was specifically and irreversibly inactivated by cell extracts.


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