The isolation and partial characterization of a glycoprotein isolated from human gastric aspirates and from extracts of gastric mucosae

The isolation and partial characterization of a glycoprotein isolated from individual gastric aspirates and extracts of gastric mucosae solubilized with N-acetylcysteine is described.The isolated glycoproteins and the glycoproteins from proteolysed gastric aspirates showed virtually the same carbohydrate and amino acid composition. The results indicate that they consist of a protein core to which are attached carbohydrate side-chains composed of four sugars: N-acetylgalactosamine N-acetylglucosamine, galactose, fucose showing a ratio of 1 : 3 : 4 : 2. Superimposed on this basic structure were additional sugar residues, the blood-group determinants. The results also suggest that the carbohydrate side-chains are linked by an alkali-labile O-glycosidic linkage to the threonine and serine residues of the protein core, N-acetylgalactosamine forming the link.