Structure of the asn-linked oligosaccharides of apolipophorin III from the insect Locusta migratoria. Carbohydrate-linked 2-aminoethylphosphonate as a constituent of a glycoprotein.

The primary structures of the N-linked carbohydrate chains of apolipophorin III from the insect Locusta migratoria have been determined. The glycoprotein was completely deglycosylated with peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F. Released oligosaccharides were separated from the remaining protein using gel-permeation chromatography on Bio-Gel P-100. Purification of the carbohydrate chains was achieved by a combination of FPLC anion-exchange chromatography on Mono-Q and amine adsorption HPLC on Lichrosorb-NH2. The structures of the carbohydrate chains were deduced with a combination of fast atom bombardment mass spectrometry, 1H- and 31P-NMR spectroscopy, and methylation analysis. The majority of the carbohydrate chains contains 2-aminoethylphosphonate (AEP), which is linked to the 6-position of Man and/or GlcNAc. L. migratoria apolipophorin III is the first example of a glycoprotein containing carbohydrate-linked 2-aminoethylphosphonate. The structures of the major oligosaccharides were established to be the following: [formula: see text]