We previously identified an activity in the soluble fraction of the yeast Saccharomyces cerevisiae that is a candidate for catalyzing the proteolytic maturation of farnesylated -CXXX precursor polypeptides. We describe here a 1259-fold purification of this activity by chromatography on DEAE-cellulose, hydroxylapatite, phenyl-Sepharose, and Sephacryl S-200. Sodium dodecyl sulfate gel electrophor...