Evidence for non-vacuolar proteolytic catabolite inactivation of yeast fructose-1,6-bisphosphatase

Immunoblotting was used to study whether proteolytic degradation of fructose-1,6-bisphosphatase (EC 3.1.3.11) in yeast cells during catabolite inactivation occurs intra- or extravacuolarly. The 40-kDa subunits of both the phosphorylated and the non-phosphorylated fructose-1,6-bisphosphatase are rapidly degraded by an extract from isolated vacuoles to a 32-kDa intermediate which accumulates and is then slowly further degraded. However, in intact cells, neither the 32-kDa nor any other intermediate reacting with the fructose-1,6-bisphosphatase antibodies is observed following glucose-induced degradation of the enzyme. These observations are discussed as evidence against intravacuolar degradation of fructose-1,6-bisphosphatase during proteolytic catabolite inactivation.