Isolation and characterization of deaminated neuraminic acid-rich glycoprotein (KDN-gp-OF) in the ovarian fluid of rainbow trout (Salmo gairdneri).

A novel highly acidic glycoprotein (deaminated neuraminic acid-rich glycoprotein; KDN-gp) was first discovered as an integral component of the vitelline envelope of rainbow trout eggs [Inoue, S., et al. (1988) Biochem. Biophys. Res. Commun. 153, 172-176]. Another member of this class of glycoprotein has now been found in the ovarian (or coelomic) fluid of ovulating rainbow trout. This ovarian fluid KDN-glycoprotein is designated as KDN-gp-OF and its amino acid and carbohydrate compositions were compared with those of the vitelline envelope KDN-gp (KDN-gp-VE). KDN-gp-OF was similar to KDN-gp-VE in the carbohydrate composition and molecular weight. However, a small but definite difference in amino acid composition and the molecular weight range was found between KDN-gp-OF and KDN-gp-VE. The results suggest that in KDN-gp-OF some peptide sequences presumably present at either the C- or N-terminus are deleted from KDN-gp-VE. Possible biological function of KDN-gp-OF is discussed.