Glutamine synthetase (GS) is a key enzyme involved in nitrogen metabolism that performs the essential biochemical function of ammonium assimilation and glutamine synthesis. The enzyme and its isoforms are present universally in all organisms and display diverse regulatory patterns. In this study, we have analyzed some sequences upstream and downstream the initiation codon of the structural gene of GS (glnA) to show that these sequences are involved in regulation and stable expression of the enzyme. GS is known to be regulated by adenylylation-deadenylylation cascade in some organisms. Analysis of the adenylylation site from several organisms revealed that the site could also be deciphered from those organisms where regulation of the enzyme is not known by adenylylation. The adenylylation site was mutated by the use of Swiss-PdbViewer and possible reasons were assigned to the functional and nonfunctional properties of this site in various organisms. This analysis has also helped in assigning functional relationships to some conserved sequences within and in the proximity of the glnA gene.