Unbranched polylactosamino-O-glycans on human skim milk mucins exhibit Gal beta(1-4)GlcNAc beta(1-6) repeating units.

Neutral O-glycans on human skim milk mucins exhibit unique structural features, which may be summarized as follows: 1) the carbohydrate chains comprise up to 16 (or more) monosaccharide units; 2) the core structures are of the common type 2 Gal beta(1-3)[GlcNAc beta(1-6)]GalNAc; 3) the poly-N-acetyllactosamine backbones of the major glycans are unbranched; 4) the repetitive N-acetyllactosamine units of the linear species are linked by the hitherto unknown sequence GlcNAc beta(1-6)Gal rather than GlcNAc beta(1-3)Gal; 5) another major portion of mucin O-glycans represents branched isomers of the linear species containing except for their branching points at 3,6 disubstituted galactose residues the same structural elements as their unbranched counterparts; 6) fucosylation at various sites of the polyactosamine sequences yields mono-, di- and trifucosylated species; 7) fucosylation occurs predominantly at the subterminal GlcNAc and at the core-GlcNAc of the carbohydrate chain.