Isolation and characterization of surface glycopeptides from adult rat hepatocytes in an established line

The fractionation of glycopeptides isolated from the surface of an established line of adult rat hepatocytes, after 48 h metabolic labeling with [14C] glucose leads to the demonstration of the presence of two types of glycopeptides: i) O-glycopeptides containing N-acetylneuraminic acid, galactose and N-acetylgalactosamine, ii) N-glycopeptides with mannose, galactose, N-acetylgluosamine, fucose and N-acetylneuraminic acid. The former yield, by alkaline reductive degradation, a trisaccharide: sialyl-galactosyl-N-acetyl-galactosaminitol, a tetrasaccharide : di-sialyl-galactosyl-N-acetyl-galactosaminitol and a small amount of the disaccharide: galactosyl-N-acetyl-galactosaminitol. The latter are alkali-stable and can be divided by ion-exchange chromatography on DEAE-cellulose into i) acidic glycopeptides, not retained on a Concanavalin A-Sepharose column and belonging to the N-acetyllactosaminic type glycopedtides and ii) neutral glycopeptides which can be further fractionated on the Con-A-Sepharose column into non-retained glycopeptides belonging to the N-acetyllactosaminic type, and glycopeptides retained on the Sepharose-Con A column, containing only N-acetylglucosamine and mannose residues and related to the oligomannosidic type glycopeptides.