Structures of the carbohydrate moieties of secretory component purified from human milk

Abstract

Secretory component purified from human milk contains four asparagine-linked sugar chains in one molecule. The sugar chains were released from the polypeptide portion of secretory component by hydrazinolysis as oligosaccharides and fractionated by paper electrophoresis and paper chromatography. The sugar chains of secretory component show an extraordinarily high multiplicity. By sequential exoglycosidase digestion in combination with methylation analysis, more than 40 structurally different sugar chains were found. They were all of biantennary complex type with either Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNac beta 1 leads to 4GlcNAc or Man alpha 1 leads to 6(Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAc as their core portions and the multiplicity is produced by variety of the two outer chain moieties. The structures of outer chains found are GlcNAc beta 1 leads to 2, +/- NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 2, Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 2, GL beta 1 leads to 4GlcNAc beta 1 leads to 3Gal beta 1 leads to 4(+/- Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 2, NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 3 Gal beta 1 leads to 4GlcNAc beta 1 leads to 2, Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 3Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 2, and NeuAc alpha 2 leads to 6Gal beta 1 leads to 4GlcNAc beta 1 leads to 3Gal beta 1 leads to 4(Fuc alpha 1 leads to 3)GlcNAc beta 1 leads to 2.