Lack of correlation between trehalase activation and trehalose-6 phosphate synthase deactivation in cAMP-altered mutants of Saccharomyces cerevisiae |
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Authors: | Juan-Carlos Argüelles Dolores Carrillo Jerónima Vicente-Soler Francisco Garcia-Carmona Mariano Gacto |
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Institution: | (1) Departamento de Genética y Microbiologia, Facultad de Biología, Universidad de Murcia, E-30071 Murcia, Spain;(2) Departamento de Bioquimica, Facultad de Biología, Universidad de Murcia, E-30071 Murcia, Spain |
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Abstract: | 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 . |
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Keywords: | Trehalase Trehalose-6-P synthase cAMP mutants Saccharomyces cerevisiae |
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