The asparagine-linked carbohydrate of honeybee venom hyaluronidase

Abstract

Hyaluronidase from the venom of the honeybee (Apis mellifera) has been purified by gelpermeation and cation exchange chromatography. Its asparagine-linked carbohydrate chains were released from tryptic glycopeptides with N-glycosidase A and reductively aminated with 2-aminopyridine. Separation of the fluorescent derivatives by size-fractionation and reversed-phase HPLC afforded eighteen fractions which were analysed by two-dimensional HPLC mapping combined with exoglycosidase digestions. The bulk of the N-linked glycans of hyaluronidase consisted of small oligosaccharides (Man_1–3GlcNAc₂), most of which were either α1,3-monofucosylated or α1,3-(α1,6-)difucosylated at the innermost GlcNAc residue. High-mannose type structures constituted the minor fractions, together making up about 5% of the oligosaccharide pool from hyaluronidase. Four fractions, making up 8% of the N-linked glycans, contained the terminal trisaccharide GalNAcβ1-4[Fucα1-3]GlcNAcβ1- in β1,2-linkage to the core α1,3-mannosyl residue. No evidence for the presence of O-glycans or sialic acids could be found.