Sm. Schork et al., CATABOLITE INACTIVATION OF FRUCTOSE-1,6-BISPHOSPHATASE IN YEAST IS MEDIATED BY THE PROTEASOME, FEBS letters, 349(2), 1994, pp. 270-274
Fructose-1,6-bisphosphatase, a key enzyme in gluconeogenesis, undergoe
s catabolite inactivation when glucose is added to gluconeogenetically
active cells of the yeast Saccharomyces cerevisiae. Phosphorylation o
f the enzyme is followed by rapid degradation. To elucidate the cellul
ar proteolytic system involved in catabolite-triggered degradation of
fructose-1,6-bisphosphatase this event was followed in different prote
ase-deficient yeast mutants. In a mutant defective in the proteolytic
function of the vacuole the degradation rate of the enzyme is not dimi
nished. In contrast mutants defective in the proteolytic activity of t
he proteasome exhibit a strongly reduced glucose-induced degradation o
f fructose-1,6-bisphosphatase as compared to their isogenic wild-type
counterparts. Our studies suggest that catabolite inactivation of fruc
tose-1,6-bisphosphatase occurs in the cytosol, the degradation event b
eing mediated by the proteasome. An explanation is presented which tri
es to resolve the formerly conflicting results, which suggested glucos
e-triggered uptake of fructose-1,6-bisphosphatase into the vacuole fol
lowed by vacuolar proteolysis.