O-glycosidic linkage in glycoprotein isolates from human ocular mucus

Alkaline beta-elimination and sodium borohydride reduction were used to study the O-glycosidic linkage of N-acetylgalactosamine to seryl and threonyl residues in the high molecular weight crude glycoprotein fractions isolated from human ocular mucus. Pure mucins, BSM and OSM, were used as models. Data are presented for the existence of such O-glycosidic linkages. It was estimated from sodium borohydride reaction that at least 22% of the total peptide bonded hydroxyamino acid residues are linked O-glycosidically. These findings, as a continuation of our previous work on the isolation and chemical characterization of human ocular mucus, provided additional evidence of the mucin nature of the glycoprotein isolates.