β-N-Acetylhexosaminidase-catalysed synthesis of non-reducing oligosaccharides

A large panel of fungal β-N-acetylhexosaminidases was tested for the regioselectivity of the β-GlcNAc transfer onto galacto-type acceptors (d-galactose, lactose, 2-acetamido-2-deoxy-d-galactopyranose). A unique, non-reducing disaccharide β-d-GlcpNAc-(1→1)-β-d-Galp and trisaccharides β-d-GlcpNAc-(1→4)-β-d-GlcpNAc-(1→1)-β-d-Galp, β-d-Galp-(1→4)-β-d-Glcp-(1→1)-β-d-GlcpNAc and β-d-Galp-(1→4)-α-d-Glcp-(1→1)-β-d-GlcpNAc were synthesised under the catalysis of the β-N-acetylhexosaminidase from the Aspergillus flavofurcatis CCF 3061 with d-galactose and lactose as acceptors. The use of 2-acetamido-2-deoxy-d-galactopyranose as an acceptor with the β-N-acetylhexosaminidases from A. flavofurcatis CCF 3061, A. oryzae CCF 1066 and A. tamarii CCF 1665 afforded only β-d-GlcpNAc-(1→6)-d-GalpNAc.