Binds to oocyte zona pellucida in vivo. May play a role in the fertilization process and/or early embryonic development. Might act as a protective secretion influencing the first steps of the reproductive process necessary for the normal triggering of fertilization and early embryonic development. Secretory granules. Oviduct. Highly O-glycosylated and also N-glycosylated. Belongs to the glycosyl hydrolase 18 family.