C. Van Vaeck et al., Analysis and modification of trehalose 6-phosphate levels in the yeast Saccharomyces cerevisiae with the use of Bacillus subtilis phosphotrehalase, BIOCHEM J, 353, 2001, pp. 157-162
In the yeast Saccharomyces cerevisiae, trehalose is synthesized by the treh
alose synthase complex in two steps. The Tps1 subunit catalyses the formati
on of trehalose 6-phosphate (Tre6P), which is dephosphorylated by the Tps2
subunit, Tps1 also controls sugar influx into glycolysis; a tps1 deletion s
train is therefore unable to grow on glucose. It is unclear whether this re
gulatory function of Tps1 is mediated solely by Tre6P or also involves the
Tps1 protein. We have developed a novel sensitive and specific assay method
for Tre6P. It is based on the conversion of Tre6P into glucose and glucose
6-phosphate with purified phosphotrehalase from Bacillus subtilis. The glu
cose formed is measured with the glucose-oxidase/peroxidase method. The Tre
6P assay is linear in the physiological concentration range. The detection
limit, including the entire extraction procedure, is 15 nmol, corresponding
to an intracellular concentration of 100 muM. To modify Tre6P levels 61 vi
vo, we expressed B. subtilis phospho-trehalase in yeast. The enzyme is func
tional because it rescues the temperature-sensitive growth defect of a tps2
Delta strain and drastically lowers Tre6P levels in this strain. However,
phospho trehalase expression remains without effect on TreBP levels in wild
-type strains, as opposed to overexpression of Tps2. Because Tps2 is part o
f the TreBP synthase (TPS) complex and because this complex is destabilized
in tps2 deletion strains, these results can be explained if Tre6P is seque
stered within the TPS complex in wild-type cells. The very low levels of Tr
e6P in cells overexpressing Tps2 have a limited effect on sugar phosphate a
ccumulation and do not prevent growth on glucose. Taken together, our resul
ts support a model in which the regulatory function of Tps1 on sugar influx
is mediated both by the Tps1 protein and by Tre6P.