Lack of correlation between trehalase activation and trehalose-6 phosphate synthase deactivation in cAMP-altered mutants of Saccharomyces cerevisiae.
The rise in cAMP level that follows the addition of glucose or 2,4-dinitrophenol (DNP) to stationary-phase 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 (tpkw1 BCY1 strains) or cAMP-independent (tpk1w1 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".
Argüelles
J C
JC
Departamento de Genética y Microbiología, Facultad de Biología, Universidad de Murcia, Spain.
Carrillo
D
D
Vicente-Soler
J
J
García-Carmona
F
F
Gacto
M
M
D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D005947:Glucose / Q000378:metabolism; D005964:Glucosyltransferases / Q000037:antagonists & inhibitors* / Q000235:genetics; D007700:Kinetics; D009154:Mutation; D014198:Trehalase / Q000235:genetics / Q000378:metabolism*
D000242:Cyclic AMP; D005964:Glucosyltransferases; C023180:trehalose-6-phosphate synthase; D014198:Trehalase; D005947:Glucose