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. Differentially expressed in the oviductal pars recta (PR) region. The catalytically inactive 108 kDa form is processed both N- and C-terminally to give rise to catalytically active and inactive forms. Belongs to the peptidase S1 family.