Primary Structure of the N‐Glycosidically Linked Sialoglycans of Secretory Immunoglobulins A from Human Milk

Abstract

The alkali‐stable sialoglycopeptides of secretory immunoglobulins A from human milk have been separated from the alkali‐labile glycopeptides by gel filtration and from the asialoglycopeptides by ion‐exchange chromatography. The structures of five of them have been determined on the basis of the results obtained by methylation analysis, mass spectrometry and 360 MHz 1H‐NMR spectroscopy. For glycopeptide B, the following structure has been found: (Formula Presented.) The other glycopeptides can be considered as extensions of this structure. The following extensions to Gal‐6′ are proposed: NeuAc(α2 – 6) (glycopeptide A), Gal(β1 – 3) (glycopeptide D) and Fuc(α1 – 6) (glycopeptide E). Furthermore, in glycopeptide C a fucose residue in (α1 – 3) linkage to GlcNAc‐5′ could be traced. Copyright © 1982, Wiley Blackwell. All rights reserved