The control of glycogen metabolism in yeast

1. Interconversion in vivo of glycogen synthase and glycogen phosphorylase induced by glucose, a nitrogen source or uncouplers

Authors

  • Jean FRANÇOIS,

    1. Laboratoire de Chimie Physiologique, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology, Brussels
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  • Maria Elena VILLANUEVA,

    1. Laboratoire de Chimie Physiologique, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology, Brussels
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  • Henri-Géry HERS

    Corresponding author
    1. Laboratoire de Chimie Physiologique, Université Catholique de Louvain and International Institute of Cellular and Molecular Pathology, Brussels
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Correspondence to H.-G. Hers, Laboratoire de Chimie Physiologique de l'Université Catholique de Louvain, UCL 7539, Avenue Hippocrate 75, B-1200 Bruxelles, Belgium

Abstract

The addition of glucose to a suspension of yeast initiated glycogen synthesis and ethanol formation. Other effects of the glucose addition were a transient rise in the concentration of cyclic AMP and a more prolonged increase in the concentration of hexose 6-monophosphate and of fructose 2,6-bisphosphate. The activity of glycogen synthase increased about 4-fold and that of glycogen phosphorylase decreased 3–5-fold. These changes could be reversed by the removal of glucose from the medium and induced again by a new addition of the sugar. These effects of glucose were also obtained with glucose derivatives known to form the corresponding 6-phosphoester. Similar changes in glycogen synthase and glycogen phosphorylase activity were induced by glucose in a thermosensitive mutant deficient in adenylate cyclase (cdc35) when incubated at the permissive temperature of 26°C, but were much more pronounced at the nonpermissive temperature of 35°C. Under the latter condition, glycogen synthase was nearly fully activated and glycogen phosphorylase fully inactivated. Such large effects of glucose were, however, not seen in another adenylate-cyclase-deficient mutant (cyr1), able to incorporate exogenous cyclic AMP.

When a nitrogen source or uncouplers were added to the incubation medium after glucose, they had effects on glycogen metabolism and on the activity of glycogen synthase and glycogen phosphorylase which were directly opposite to those of glucose. By contrast, like glucose, these agents also caused, under most experimental conditions, a detectable rise in cyclic AMP concentration and a series of cyclic-AMP-dependent effects such as an activation of phosphofructokinase 2 and of trehalase and an increase in the concentration of fructose 2,6-bisphosphate and in the rate of glycolysis. Under all experimental conditions, the rate of glycolysis was proportional to the concentration of fructose 2,6-bisphosphate. Uncouplers, but not a nitrogen source, also induced an activation of glycogen phosphorylase and an inactivation of glycogen synthase when added to the cdc35 mutant incubated at the restrictive temperature of 35°C without affecting cyclic AMP concentration.

Abbreviations
Fru(2,6)P2

fructose 2,6-bisphosphate

Glc6P

glucose 6-phosphate

Glc1P

glucose 1-phosphate

Fru6P

fructose 6-phosphate

Fru(1,6)P2

fructose glucose 1,6-bisphosphate

PFK 1

phosphor-fructo 1-kinase

PFK 2

phosphofructo 2-kinase

Enzymes
 

6-Phosphofructo 1-kinase (EC 2.7.1.11)

 

6-phosphofructo 2-kinase (EC 2.7.1.105)

 

trehalase (EC 3.2.1.28)

 

glycogen synthase (EC 2.4.1.11)

 

glycogen phosphorylase (EC 2.4.1.1)

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