Mediates gamete interaction by affecting the vitelline coat. Preferential cleavage at 371-Gly-Ser-Arg-|-Trp-374 of glycoprotein gp43 in Xenopus laevis coelemic egg envelope to yield gp41. Expressed specifically in the cells lining the bottom of epithelial folds in the oviductal pars recta. By human chorionic gonadotropin (HCG). The catalytically inactive 107 kDa form is processed both N- and C-terminally to give rise to the 66 kDa catalytically active form and inactive forms of 82 kDa and 59 kDa. Belongs to the peptidase S1 family.