Ammonia assimilation in the fission yeast Schizosaccharomyces pombe 972.
Glutamine synthetase (GS) activity of Schizosaccharomyces pombe 972 was high in ammonia-limited cultures, low in phosphate- and sulphate-limited cultures and not detected in glucose-limited cultures. When ammonia was 'pulsed' into an ammonia-limited culture then GS activity decreased at a rate faster than that calculated if enzyme synthesis ceased and enzyme was diluted out by growth. Enzyme activity increased in ammonia-starved, phosphate-limited cultures and in the ammonia 'pulse' system when the added ammonia had been utilised. These increases in enzyme activity were prevented by the presence of 100 mug/ml cycloheximide. GS activity was inversely related to the intracellular concentration of glutamate.
Ammonia assimilation in the fission yeast Schizosaccharomyces pombe 972. Glutamine synthetase (GS) activity of Schizosaccharomyces pombe 972 was high in ammonia-limited cultures, low in phosphate- and sulphate-limited cultures and not detected in glucose-limited cultures. When ammonia was 'pulsed' into an ammonia-limited culture then GS activity decreased at a rate faster than that calculated if enzyme synthesis ceased and enzyme was diluted out by growth. Enzyme activity increased in ammonia-starved, phosphate-limited cultures and in the ammonia 'pulse' system when the added ammonia had been utilised. These increases in enzyme activity were prevented by the presence of 100 mug/ml cycloheximide. GS activity was inversely related to the intracellular concentration of glutamate.