Correlation of glutamine synthetase activity with cell magnesium concentration during cell division in yeast synchronized by induction

Synchronization of cell division in the fission yeast Schizosaccharomyces pombe and the budding yeast Kluyveromyces fragilis was achieved by induction using the DNA synthesis inhibitor 2'-deoxyadenosine and by a magnesium-exhaustion technique. The activity of glutamine synthetase in these synchronized cultures oscillated. Variations in the intracellular magnesium concentration were also observed, and peaks in magnesium concentration correlated with peaks in enzyme activity. We suggest that the enzyme from yeast is unstable and that its activity is regulated in vivo by changes in the intracellular concentration of magnesium.