IDENTIFICATION AND ACTIVATION OF PROFOLLIPSIN, A LATENT PRECURSOR FORM OF PORCINE FOLLIPSIN

A latent protease has been identified in column fractions obtained dur ing the purification of the porcine ovarian serine protease follipsin. The latent enzyme was readily activated by trypsin treatment. The try psin-activated enzyme was purified using a benzamidine-Sepharose 6B co lumn and was shown to be composed of two distinct, covalently associat ed polypeptides with M-r of 45000 and 32000. This polypeptide chain co mposition, together with its substrate specificity, inhibition profile using various protease inhibitors, cross-reactivity with anti-follips in antibody, and ability to activate single-chain precursor tissue pla sminogen activator, indicated its identity as porcine follipsin. The a ctivation of the enzyme with trypsin was found to occur by the hydroly sis of an internal peptide bond resulting in a two-chain structure. Th us, we conclude that the latent enzyme is the inactive precursor form (profollipsin) of follipsin. The present study also shows that the fol licular fluid of porcine ovary contains a profollipsin-activating enzy me activity.