NEW APPROACH TOWARDS DEGLYCOSYLATION OF SIALOGLYCOPROTEINS AND MUCINS

A modified procedure for chemical deglycosylation of glycoproteins con taining sialylated and/or O-linked oligosaccharides, using anhydrous t rifluoromethane sulfonic acid (TFMSA) is described. Although sialic ac id residues are acid labile, it has been known that anhydrous TFMSA do es not effectively remove carbohydrate side chains from glycoproteins if they are sialylated. In this procedure, sialic acid residues were r emoved by mild acid hydrolysis and the desialylated glycoprotein was t reated with anhydrous TFMSA reagent under conditions which remove all the carbohydrate residues except the core D-GalNAc linked to serine/th reonine. The core D-GalNAc residues were removed by reacting the glyco protein with periodate followed by a second treatment with anhydrous T FMSA; this procedure gave a completely deglycosylated protein. The pro tein thus obtained was soluble in aqueous buffers and useful for bioch emical and biophysical studies. The method was successfully employed t o isolate polypeptides from al-acid glycoprotein (N-linked), fetuin, c anine tracheal mucin and gastric mucin.