The purification of glutamine synthetase from Azotobacter and other procaryotes by blue sepharose chromatography

We report the facile purification of glutamine synthetase (L-glutamate: ammonia ligase (adenosine 5'-diphosphate-forming), EC 6.3.1.2) in both the adenylylated and unadenylylated form, from Azotobacter vinelandii ATCC 12837. A general affinity column, which used as an affinity ligand Reactive blue 2 dye (Cibacron blue) covalently linked to Agarose, was employed as an efficient first step of purification. Further purification to electrophoretic homogeneity employed DEAE-cellulose chromatography and an additional Affigel chromatographic step. The method was used successfully to prepare glutamine synthetase from Escherichia coli, Rhodopseudomonas sphaeroides and Anabaena sp. strain CA.