, Volume 23, Issue 5-6, pp 382-387

Lack of correlation between trehalase activation and trehalose-6 phosphate synthase deactivation in cAMP-altered mutants of Saccharomyces cerevisiae

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The rise in cAMP level that follows the addition of glucose or 2,4-dinitrophenol (DNP) to stationaryphase cells of Saccharomyces cerevisiae was accompanied by a marked activation of trehalase (3-fold increase) and a concomitant deactivation of trehalose-6 phosphate synthase (50% of the basal levels). In glucose-grown exponential cells, which are deficient in glucose-induced cAMP signalling, the addition of glucose also prompted a decrease in trehalose-6 phosphate synthase, but had no effect on trehalase activity. Mutants defective in the RAS-adenylate cyclase pathway (ras1 ras2 bcy1 strain), as well as mutants containing greatly reduced protein kinase activity either cAMP-dependent (tpk w1 BCY1 strains) or cAMP-independent (tpk1 w1 bcy1 strains), were unable to show glucose- or DNP-induced trehalase activation but still displayed a clear decrease in trehalose-6 phosphate synthase activity upon addition of these compounds. These data suggest that the activity of trehalose-6 phosphate synthase, as opposed to that of trehalase, is not controlled by the cAMP signalling pathway “in vivo”. Trehalose-6 phosphate synthase was competitively inhibited by glucose (Ki=15 mM) and resulted unaffected by ATP in assays performed “in vitro”.