Glycosidase-catalysed oligosaccharide synthesis: preparation of N-acetylchitooligosaccharides using the β-N-acetylhexosaminidase of Aspergillus oryzae

Article abstract of DOI:10.1016/0008-6215(95)00302-9

The β-N-acetylhexosaminidase of Aspergillus oryzae catalyses the formation of 2-acetamido-4-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-deoxy-D-glucopyranose (di-N-acetylchitobiose) and 2-acetamido-6-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-2-deoxy-D-glucopyranose from p-nitrophenyl 2-acetamido-2-deoxy-β-D-glucopyranoside and 2-acetamido-2-deoxy-D-glucopyranose.The ratio of the two disaccharides is time-dependent.The ratio of (1<*>4)- to (1<*>6)-isomers is a maximum (ca. 9:1) at the point of disappearance of the glycosyl donor.If left to evolve, the ratio changes to 92:8 in favour of the (1<*>6)-isomer.Either the (1<*>4)- or the (1<*>6)-isomer can be isolated by treating the appropriately enriched disaccharide mixture with the β-N-acetylhexosaminidase of Jack bean (Canavalia ensiformis) or the β-N-acetylhexosaminidase of A. oryzae, respectively.Di-N-acetylchitobiose is an efficient donor of 2-acetamido-2-deoxy-D-glucopyranosyl units in reactions catalysed by the N-acetylhexosaminidase of A. oryzae.Di-N-acetylchitobiose itself acts as acceptor to give tri-N-acetylchitotriose .As the trisaccharide accumulates it, in turn, acts as acceptor giving tetra-N-acetylchitotetraose .The product mixture consisting of mono-, di-, tri-, and tetra-saccharides is conveniently separated by charcoal-Celite chromatography. Keywords: Glycosidase; N-acetylhexosaminidase; Chitooligosaccharides; Enzymatic synthesis.