Evidence for trehalose-6-phosphate-dependent and -independent mechanisms in the control of sugar influx into yeast glycolysis.
In the yeast Saccharomyces cerevisiae, 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 byp 1-3 allele of GGS1/TPS1. The byp 1-3 tps2 delta 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 tps 2 delta 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 byp 1-3 tps2 delta 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.
Hohmann
S
S
Laboratorium voor Moleculaire Celbiologie, Katholieke Universiteit Leuven, Flanders, Belgium.
Bell
W
W
Neves
M J
MJ
Valckx
D
D
Thevelein
J M
JM
D000431:Ethanol / Q000378:metabolism; D005632:Fructose / Q000378:metabolism; D017353:Gene Deletion; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology; D006019:Glycolysis; D006026:Glycoside Hydrolases / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000378:metabolism*; D013172:Spores, Fungal / Q000502:physiology; D013403:Sugar Phosphates / Q000235:genetics / Q000378:metabolism*; D014199:Trehalose / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D043324:beta-Fructofuranosidase
D013403:Sugar Phosphates; D005632:Fructose; D000431:Ethanol; C082722:trehalose-6-phosphate; D014199:Trehalose; D006593:Hexokinase; D006026:Glycoside Hydrolases; D043324:beta-Fructofuranosidase; D005947:Glucose