In vivo biosynthesis of the vacuolar proteinases A and B in the yeast Saccharomyces cerevisiae.

Proteinase A and proteinase B, two vacuolar enzymes in Saccharomyces cerevisiae, are synthesized as larger precursors with apparent molecular weights of approximately 52,000 and 42,000, respectively. These precursor molecules are processed to their mature forms of 42,000 molecular weight for proteinase A and 33,000 molecular weight for proteinase B. In the presence of tunicamycin, an inhibitor of the synthesis of protein-asparagine linked carbohydrate moieties, two smaller molecular forms each of precursor and mature proteinase A were synthesized, indicating that proteinase A contains N-linked carbohydrate which is apparently not required for processing. Tunicamycin interferes also with the glycosylation of the proteinase B precursor, whereas no unglycosylated mature proteinase B could be detected.