VACUOLAR CARBOXYPEPTIDASE-Y OF SACCHAROMYCES-CEREVISIAE IS GLYCOSYLATED, SORTED AND MATURED IN THE FISSION YEAST SCHIZOSACCHAROMYCES-POMBE

Vacuolar carboxypeptidase Y of Saccharomyces cerevisiae (CPYSC) has been expressed in a Schizosaccharomyces pombe strain devoid of the endogenous equivalent peptidase, employing a 2 mu derived plasmid. Immunoblot analysis revealed that CPYSC produced in the fission yeast has a higher molecular mass than mature CPYSC produced by the budding yeast. CPYSC is glycosylated when expressed in S. pombe and uses four N-linked glycosylation sites as shown by endoglycosidase H digestion. Carbohydrate removal leads to a protein moiety which is indistinguishable in size from deglycosylated CPYSC produced by S. cerevisiae. CPYSC isolated from S. pombe soluble extracts is enzymatically active and thus is presumed to undergo correct proteolytic maturation. Subcellular fractionation experiments showed a cofractionation of CPYSC with the S. pombe endoproteinases PrA and PrB, suggesting that the protein is correctly sorted to the vacuole and that these peptidases might be responsible for zymogen activation.