A selective method for sequential splitting of O- and N-linked glycans from N,O-glycoproteins.

O-Linked oligosaccharides from N,O-glycoproteins were selectively split off by treatment with alkaline sodium borohydride in the presence of cadmium salt. The side reaction of reductive cleavage of N-glycosylamide and peptide bonds, observed under standard conditions of splitting of O-linked chains (M NaBH4 and 50mM NaOH, 16 h, 50 degrees), was inhibited by addition of 50-10 mM cadium acetate and 5-10mM EDTA.Na4, as shown by treatment of model compounds and several glycoproteins (ovomucoid, group-specific glycoproteins H and B, fetuin, and asialofetuin). This treatment, in combination with the previously developed procedure for the release of the N-linked oligosaccharide chains by lithium borohydride, allows a sequential, selective cleavage of O-, and then N-linked oligosaccharides from N,O-glycoproteins by chemical methods.