Structure determination of the major N‐ and O‐linked carbohydrate chains of the β subunit from equine chorionic gondotropin

Abstract

The carbohydrate moieties of equine chorionic gonadotropin α and β subunits were released from the protein backbones by successive treatments with peptide‐(N‐acetyl‐β‐glucosaminyl)asparagine amidase F and alkaline borohydride and then fractionated by FPLC and HPLC. The major N‐ and O‐linked glycans of the β subunit were characterized by 500‐MHz 1H‐NMR spectroscopy, showing a remarkable structural heterogeneity for the N‐glycosidically linked chains, comprising mono‐,di‐, tri‐ and tri′‐antennary N‐acetyllactosamine type of glycans, being partly α1‐6 fucosylated at the Asn‐bound GlcNAc residue and having α2‐6 and α2‐3 linked N‐acetyl‐ and N‐acetyl‐4‐O‐acetylneuraminic acid residues as sialic acid constituents. Significant differences in this respect were detected for the partially characterized glycans of the α subunit. The major part of the O‐linked carbohydrate chains, occurring solely in the β subunit, is formed by tri‐, tetra‐, penta‐ and hexa‐saccharides. There are indications for the presence of oligo(N‐acetyllactosamine) units in both the N‐ and O‐linked glycans of the β subunit. Copyright © 1990, Wiley Blackwell. All rights reserved