Isolation and Characterization of Alkali-Labile Oligosaccharide Units from Porcine Erythrocyte Glycophorin

The oligosaccharide units of glycophorin isolated from porcine erythrocyte membranes were released by alkaline borohydride treatment and purified by gel filtration and ion-exchange chromatography. Structures of the O-glycosidic oligosaccharides were determined by methylation analysis, the methylated sugar being identified by gas-liquid chromatography-mass spectrometry and nitrous acid deamination after hydrazinolysis. The major oligosaccharide was a trisaccharide, Gal(1⇒3)[Neu-NGly(2⇒6)]GalNAc. The other oligosaccharides were larger and contained GlcNAc. One was a pentasaccharide, Gal(1⇒3)Gal(1⇒4)GlcNAc(1⇒3)Gal(1⇒3)GalNAc. The structure of the trisaccharide was also analyzed by direct-probe mass spectrometry of the permethylated derivative, and the result obtained was consistent with the proposed structure.