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Evidence for trehalose‐6‐phosphate‐dependent and ‐independent mechanisms in the control of sugar influx into yeast glycolysis
Author(s) -
Hohmann Stefan,
Bell Walter,
NevesA Maria Jose,
Valckx Dirk,
Thevelein Johan M.
Publication year - 1996
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1996.tb02539.x
Subject(s) - trehalose , biology , glycolysis , sugar phosphates , sugar , biochemistry , yeast , mutant , fructose , saccharomyces cerevisiae , metabolism , enzyme , gene
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 tps2 Δ 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 tps2 Δ 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 tps2 Δ. 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.