Open AccessThe carbohydrate chains of the β subunit of human chorionic gonadotropin produced by the choriocarcinoma cell line BeWo
Author(s) -
HÄRRD Karl,
DAMM Jan B. L.,
SPRUIJT Mark P. N.,
BERGWERFF Aldert A.,
KAMERLING Johannis P.,
DEDEM Gijs W. K.,
VLIEGENTHART Johannes F. G.
Publication year - 1992
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1992.tb16843.x
Subject(s) - chemistry , exoglycosidase , sialoglycoprotein , asparagine , human chorionic gonadotropin , carbohydrate , stereochemistry , glycan , biochemistry , sialic acid , glycoprotein , amino acid , hormone
The N‐linked carbohydrate chains of the β subunit of human chorionic gonadotropin (hCG‐β) isolated from the culture fluid of the choriocarcinoma cell line BeWo were released enzymatically by peptide‐ N 4 ‐( N ‐acetyl‐β‐glucosaminyl)asparagine amidase F. Subsequently, the O‐linked oligosaccharides were split off from the N ‐deglycosylated protein by mild alkaline borohydride treatment. The carbohydrate chains were purified in their intact sialylated forms by FPLC anion‐exchange chromatography on Mono Q, HPLC on Lichrosorb‐NH 2 , and high‐pH anion‐exchange chromatography on CarboPac PA1. 1 H‐NMR spectroscopic analysis of the major fractions demonstrates the occurrence of the following sialylated diantennary and triantennary N‐linked oligosaccharides. Residues not written in bold letters are variably present.The incidence of triantennary carbohydrate chains is much higher than in normal urinary hCG‐β (26% vs 2%). The same holds for the α1–6‐fucosylation of the asparagine‐bound GlcNAc (95% vs 42%). The presence of a bisecting GlcNAc and the occurrence of α2–6‐linked Neu5Ac in the most abundant N ‐glycans, are new features for hCG‐β. The major O‐linked carbohydrate chains identified are the tetrasaccharide Neu5Acα2–3Galβ1‐3(Neu5Acα2–6)GalNAc‐ol and the hexasaccharide Neu5Acα2–3Galβ1–4GlcNAcβ1–6(Neu5‐Acα2–3Galβ1–3)GalNAc‐ol, both also found in normal urinary hCG. In addition, two novel O ‐glycans were characterized: