Glutamine Synthetase of Streptomyces cattleya: Purification and Regulation of Synthesis

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Abstract
Glutamine synthetase (GS) from S. cattleya was purified using a single affinity-gel chromatography step, and some of its properties were determined. Levels of GS in S. cattleya cells varied by a factor of 8 depending upon the source of N. in the growth medium. Of 24 N sources examined, only glutamine or NH4Cl utilization resulted in very low GS activity. Addition of NH4Cl to a culture with high GS levels appeared to stop further synthesis and resulted in a progressive decrease in the specific activity of the enzyme. The GS inhibitor methionine sulfoximine (MSX) inhibited GS activity but had no effect on exponentially growing cells. The presence of MSX either lengthened or shortened the period between spore inoculation and initiation of exponential growth, depending on the source of N. In glutamine minimal medium MSX produced earlier and more efficient spore germination while in glutamate or nitrate minimal medium germination was delayed by its presence.