Trisaccharide synthesis by glycosyl transfer from p-nitrophenyl β-d-N-acetylgalactosaminide on to disaccharide acceptors catalysed by the β-N-acetylhexosaminidase from Aspergillus oryzae

The β-N-acetylhexosaminidase from Aspergillus oryzae catalysed the transfer of β-d-N-acetylgalactosaminyl residues from p-nitrophenyl β-d-N-acetylglucosaminide on to disaccharide acceptors consisting of thioethyl glycosides of α-d-Glc-(1 → 4)-β-d-Glc, β-d-Glc-(1 → 4)-β-d-Glc and β-d-Glc-(1 → 6)-β-d-Glc. The principle of ‘anomeric control’ was exemplified by the results which showed that an α-linkage between the units of the acceptor favoured exclusively the formation of a new (1 → 4)-linkage, whereas the β-configuration in the acceptor led to a mixture of (1 → 4)- and (1 → 3)-linked products, as observed for simple glycosides of monosaccharide acceptors. With the thioethyl β-lactoside as acceptor, β-d-Gal-(1 → 6)-β-d-Gal-(1 → 4)-β-d-GlcSEt was formed, owing to the action of residual β-d-galactosidase activity in the N-acetylhexosaminidase on the thioethyl β-lactoside acting as both donor and acceptor.