Vacuolar carboxypeptidase Y of Saccharomyces cerevisiae is glycosylated,sorted and matured in the fission yeast Schizosaccharomyces pombe

Vacuolar carboxypeptidase Y of Saccharomyces cerevisiae (CPY^sc) has been expressed in a Schizosaccharomyces pombe strain devoid of the endogenous equivalent peptidase, employing a 2 μ derived plasmid. Immunoblot analysis revealed that CPY^sc produced in the fission yeast has a higher molecular mass than mature CPY^sc produced by the budding yeast. CPY^sc 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 CPY^sc produced by S. cerevisiae. CPY^sc 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 CPY^sc 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.