Isolation, characterization and nature of carbohydrate-peptide linkage of an alkali-extractable non-collagenous glycoprotein from albino rat skins.

A glycoprotein was isolated from young albino rat skins by alkali extraction under mild conditions and purified by Sephadex G-200 and DEAE-Sephadex A-50 chromatography. It was found to be homogeneous by agar gel electrophoresis. It had a molecular weight of approximately 90,000 and contained galactose, mannose, fucose, N-acetylglucosamine, N-acetylgalactosamine and sialic acids as its carbohydrate constituents. The release of sialic acids from the glycoprotein by neuraminidase indicated their terminal positions in the carbohydrate chains. The glycoprotein lacked hydroxyproline which indicates its non-collagenous nature. The treatment of the glycoprotein with alkaline borohydride resulted in the decrease of threonine, serine and N-acetylgalactosamine contents. The presence of O-glycosidic linkage of N-acetylgalactosamine with serine and threonine is therefore suggested.