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Evidence for trehalose-6-phosphate-dependent and -independent mechanisms in the control of sugar influx into yeast glycolysis

Authors

  • Stefan Hohmann,

    1. Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium.
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    • Department of General and Marine Microbiology, Göteborg University, Medicinaregatan 9C, S-41390 Göteborg, Sweden.

  • Walter Bell,

    1. Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium.
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  • Maria Jose NevesA,

    1. Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium.
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  • Dirk Valckx,

    1. Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium.
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  • Johan M. Thevelein

    Corresponding author
    1. Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Kardinaal Mercierlaan 92, B-3001 Leuven-Heverlee, Flanders, Belgium.
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Summary

In the yeast Saccharomyces cerevisíae, trehalose-6-phosphate (tre-6-P) synthase encoded by GGS1/TPS1, is not only involved in the production of trehalose but also in restriction of sugar influx into glycolysis in an unknown fashion; it is therefore essential for growth on glucose or fructose. In this work, we have deleted the TPS2 gene encoding tre-6-P phosphatase in a strain which displays very low levels of Ggs1/Tps1, as a result of the presence of the byp1-3 allele of GGS1/TPS1. The byp1-3 tps2Δ double mutant showed elevated tre-6-P levels along with improved growth and ethanol production, although the estimated concentrations of glycolytic metabolites indicated excessive sugar influx. In the wild-type strain, the addition of glucose caused a rapid transient increase of tre-6-P. In tps2Δ mutant cells, which showed a high tre-6-P level before glucose addition, sugar influx into glycolysis appeared to be diminished. Furthermore, we have confirmed that tre-6-P inhibits the hexokinases in vitro. These data are consistent with restriction of sugar influx into glycolysis through inhibition of the hexokinases by tre-6-P during the switch to fermentative metabolism. During logarithmic growth on glucose the tre-6-P level in wild-type cells was lower than that of the byp1-3 tps2Δ. mutant. However, the latter strain arrested growth and ethanol production on glucose after about four generations. Hence, other mechanisms, which also depend on Ggs1/Tps1, appear to control sugar influx during growth on glucose. In addition, we provide evidence that the requirement for Ggs1/Tps1 for sporulation may be unrelated to its involvement in trehalose metabolism or in the system controlling glycolysis.

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