Novel N-linked oligo-mannose type oligosaccharides containing an alpha-D-galactofuranosyl linkage found in alpha-D-galactosidase from Aspergillus niger

Abstract

Structures of oligosaccharides from Aspergillus niger alpha-D-galactosidase [EC 3.2.1.22] were studied. Purified alpha-D-galactosidase was treated with N-glycosidase F, and six kinds of oligosaccharides were isolated by gel chromatography and anion-exchange chromatography. The structures of the oligosaccharides were determined by 1H-NMR and compositional analysis to be Man5GlcNAc2, Man6GlcNAc2, Man9GlcNAc2, GlcMan9GlcNAc2, GalMan4GlcNAc2 and GalMan5GlcNAc2. From mild acid hydrolysis, methylation analysis and ROESY spectral analysis, it was ascertained that the galactosyl residue in two oligosaccharides was in the furanose form and was bound to mannose at the nonreducing end with an alpha 1-2 linkage (GalfMan4GlcNAc2 and GalfMan5GlcNAc2).