Phosphorylation and Inactivation of Yeast Fructose‐Bisphosphatase in vivo by Glucose and by Proton Ionophores

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Abstract
Addition of glucose to yeast cells causes a phosphorylation and an inactivation of the gluconeogenic enzyme fructose-bisphosphatase [Mazón, M. J., Gancedo, J. M., and Gancedo, C. (1982) J. Biol. Chem. 257, 1128–1130], We report here that the addition of the proton ionophores 2,4–dinitrophenol and carbonylcyanide m-chlorophenylhydrazone to yeast cells produces the same effect as that of glucose. Both glucose and ionophores produced: (a) phosphorylation and inactivation of fructose-bisphosphatase, (b) an immediate rise in the intracellular concentration of cAMP, (c) an instant inhibition of the transport of amino acids driven by the membrane potential. It is proposed that the effect of glucose on fructose-bisphosphatase involves as a first step the depolarization of the plasma membrane resulting in an increase of the intracellular concentration of cAMP. This in turn would stimulate phosphorylation of fructose-bisphosphatase.