Deglycosylation of glycoproteins by trifluoromethanesulfonic acid

A new method for the chemical deglycosylation of glycoproteins is described. Treatment of fetuin with trifluoromethanesulfonic acid at 0 or 25°C results in rapid cleavage of peripheral sugars, slow loss of serine- and threonine-linked N-acetylgalactosamine, and retention of N-glycosidically linked N-acetylglucosamine. Amino acid analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveal that the peptide backbone is left intact after reaction at 0°C for 2.5 h or at 25°C for 1 h. Treatment of ovine luteinizing hormone and human M,N-active erythrocyte sialoglycoproteins at 0°C for 3 h gives similar results. In the case of ovine luteinizing hormone, the recovered deglycosylated hormone has approximately 2% of the starting material's activity as measured in a receptor binding assay. In the case of bovine nasal septum proteoglycan, the deglycosylated core protein acts as an excellent acceptor for UDP- d-xylose:core protein β- O-xylosyltransferase. The reagent is far less toxic than HF and does not require special equipment for handling. The procedure should prove useful not only for generation of deglycosylated proteins, but also for assessment of the number of asparagine-linked saccharide chains in a glycoprotein.