Structure of the asparagine-linked sugar chains of alpha-fetoprotein purified from human ascites fluid

alpha-Fetoprotein purified from human serum was found to contain an asparagine-linked sugar chain in one molecule. The sugar chain was quantitatively released from the polypeptide moiety by hydrazinolysis and recovered as oligosaccharides after N-acetylation. The oligosaccharide mixture was separated into a neutral (N) and two acidic (A-1 and A-2) fractions by paper electrophoresis. By combination of sequential exoglycosidase digestion, methylation analysis, and concanavalin A-Sepharose column chromatography, the structures of these fractions were determined to be: Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GLcNAc beta 1 leads to 4(+/- Fuc alpha 1 leads to 6)GlcNAc; Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(+/- Fuc alpha 1 leads to 6(GlcNAc; and NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 6(NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(+/- Fuc alpha 1 leads to 6)GlcNAc.