title: Glycosidase-catalysed oligosaccharide synthesis: preparation of N-acetylchitooligosaccharides using the beta-N-acetylhexosaminidase of Aspergillus oryzae.
abstract: The beta-N-acetylhexosaminidase of Aspergillus oryzae catalyses the formation of 2-acetamido-4-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-2-deoxy-D- glucopyranose (di-N-acetylchitobiose) and 2-acetamido-6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-2-deoxy-D- glucopyranose from p-nitrophenyl 2-acetamido-2-deoxy-beta-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 (approximately 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 dissaccharide mixture with the beta-N-acetylhexosaminidase of Jack bean (Canavalia ensiformis) or the beta-N-acetylhexosaminidase of A. oryzae, respectively. Di-N-acetylchitobiose [GlcNAc(beta 1-4)GlcNAc] 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 [GlcNAc(beta 1-4)GlcNAc(beta 1-4)GlcNAc]. As the trisaccharide accumulates it, in turn, acts as acceptor giving tetra-N-acetylchitotetraose [GlcNAc(beta 1-4)GlcNAc(beta 1-4)GlcNAc(beta 1-4)GlcNAc]. The product mixture consisting of mono-, di-, tri-, and tetrasaccharides is conveniently separated by charcoal-Celite chromatography.
authors.affiliation: Department of Chemistry, University of Warwick, Coventry, UK.
authors.forename: S
authors.initials: S
authors.lastname: Singh
authors.forename: J
authors.initials: J
authors.lastname: Packwood
authors.forename: C J
authors.initials: CJ
authors.lastname: Samuel
authors.forename: P
authors.initials: P
authors.lastname: Critchley
authors.forename: D H
authors.initials: DH
authors.lastname: Crout
mesh_terms: D001236:Aspergillus oryzae / Q000201:enzymology*; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D004187:Disaccharides / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009844:Oligosaccharides / Q000096:biosynthesis* / Q000737:chemistry; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism*
chemical_list: C098470:2-acetamido-6-O-(2-acetamido-2-deoxyglucopyranosyl)-2-deoxyglucopyranose; D004187:Disaccharides; D009844:Oligosaccharides; C010913:N,N-diacetylchitobiose; D001619:beta-N-Acetylhexosaminidases