ISOLATION AND PARTIAL CHARACTERIZATION OF AN OVINE PREGNANCY-ASSOCIATED GLYCOPROTEIN (OPAG)

An ovine Pregnancy-Associated Glycoprotein (oPAG) has been isolated from fetal cotyledons by the means of ammonium sulfate precipitations and different liquid chromatographies. The bovine FAG was used as standard and tracer to monitor the oPAG in each step of isolation. Ovine FAG seems to be an heterogeneous group of glycoproteins of molecular mass ranging from 47 to 67 kD. Molecular cloning of its cDNA revealed that ovine and bovine FAG share 86 % nucleotide sequence identity and both belong to the aspartic proteinase family (greater than or equal to 50 % amino acid sequence identity to pepsin and cathepsins D and E). However neither bovine nor ovine PAGs do not appear to be enzymatically active. The oPAG's cDNA codes for a polypeptide of 382 amino acids long that is synthesized by trophoblastic binucleate cells since day 18 post conception and detected in maternal circulation since day 24 p.c. The detection of oPAG could be used for early diagnosis of pregnancy and determination of early embryonic mortality in sheep and other domestic and wild ruminants.