The isolation and partial characterization of the major bronchial glycoproteins

Partial characterization of glycoprotein obtained from mucous secretion of the bronchi and stomach has been attempted. The isolated glycoproteins and the glycoproteins from gastric aspirates showed similar carbohydrate and amino-acid composition. They consist of a protein core to which are attached carbohydrate side chains of galactose, N-acetylglucosamine and N-acetylgalactosamine in the ratio of 4 : 3 : 1. Superimposed on this structure were additional sugar residues, the blood group determinants. The carbohydrate side chains are linked by an alkali-labile O-glycosidic linkage to the threonine and serine residues of the protein core, with N-acetylgalactosamine forming the link.