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Regulation of glutamine synthetase from Saccharomyces cerevisiae by repression, inactivation and proteolysis.

par Legrain, Christiane ;Vissers, S;Dubois, Evelyne ;Legrain, M;Wiame, Jean-Marie
Référence European journal of biochemistry / FEBS, 123, 3, page (611-616)
Publication Publié, 1982-04

Article révisé par les pairs

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Résumé :

Glutamine synthetase activity is modulated by nitrogen repression and by two distinct inactivation processes. Addition of glutamine to exponentially grown yeast leads to enzyme inactivation. 50% of glutamine synthetase activity is lost after 30 min (a quarter of the generation time). Removing glutamine from the growth medium results in a rapid recovery of enzyme activity. A regulatory mutation (gdhCR mutation) suppresses this inactivation by glutamine in addition to its derepressing effect on enzymes involved in nitrogen catabolism. The gdhCR mutation also increases the level of proteinase B in exponentially grown yeast. Inactivation of glutamine synthetase is also observed during nitrogen starvation. This inactivation is irreversible and consists very probably of a proteolytic degradation. Indeed, strains bearing proteinase A, B and C mutations are no longer inactivated under nitrogen starvation.