The zona pellucida, a transparent envelope surrounding the mammalian oocyte, consists of three glycoproteins, ZPA, ZPBandZPC, andplays a role in sperm–egg interactions. In bovines, these glycoproteins cannot be separated unless the acidic N-acetyllactosamine regions of the carbohydrate chains are removed by endo-b-Galactosidase digestion. Endo-b-Galactosidase-digestedZPBretains stronger sperm-binding activity than ZPC.