PURPOSE: To provide a peptide related to clear zone PZP-3 of a pig egg, constituting the extracellular matrix surrounding the egg metrocyte, composed of a glycoprotein constituting the clear zone of a pig egg and useful as a vaccine antigen for contraception or sterilization of a mammal.

CONSTITUTION: A pig ovary is frozen in a liquid nitrogen, crushed into a powder by using a blender, homogenized in a buffer solution and then centrifuged. mRNA is extracted from the supernatant by using oligo dT cellulose, etc., and a cDNA is synthesized using the obtained mRNA as a template. The cDNA is amplified according to PCR method using a synthetic oligonucleotide composed of a part of the base sequence of a gene coding a peptide related to clear zone PZP-3 of a pig egg as a primer to obtain a gene coding the peptide related to the clear zone PZP-3 of a pig egg. The obtained gene is treated with a restriction enzyme, bonded to a vector and transferred to a host cell so as to be transformed. The resultant transformant is subsequently cultured, thus obtaining the objective peptide useful as a vaccine antigen, etc., for contraception or sterilization of a mammal including a pig.