Yeast invertase: Subcellular distribution and possible relationship between the isoenzymes

The intracellular invertase ofSaccharomyces cerevisiae is mainly found in a soluble form (91–95%), while only minor amounts are found bound to the internal (4–8%) and plasma membranes (less than 1%). In the processes of derepression or repression, inhibition of RNA or protein synthesis, or in the presence of 2-deoxy-d-glucose, the levels of the membrane-bound and external activities are modified in a way in which their relation is clear, while the soluble enzyme does not change at all. These results, together with the fact that the membrane-bound and the external enzymes are glycoproteins, suggest a precursor-product relationship between the enzymic forms.