Reverse hydrolysis reaction of chitin deacetylase and enzymatic synthesis of β-d-GlcNAc-(1→4)-GlcN from chitobiose

We found that a chitin deacetylase from Colletotrichum lindemuthianum could acetylate free amino sugar residues into N-acetylated forms in the presence of 3.0 M sodium acetate. The result was analyzed using a β-N-acetylhexosaminidase-coupled assay system with p-nitrophenyl 2-amino-2-deoxy-β-d-glucopyranosyl-(1→4)-2-acetamido-2-deoxy-β-d-glucopyranoside as the substrate, and the liberation of p-nitrophenol was observed as a consequence of enzymatic N-acetylation of the glucosamine residue at the nonreducing end of the substrate. The chitin deacetylase also acetylated chitobiose and chitotetraose as substrates, which was evidenced by the decrease in the amount of free amino sugar residues in the chitooligosaccharides. The reaction product of chitobiose after the acetylation reaction was exclusively 2-acetamido-2-deoxy-β-d-glucopyranosyl-(1→4)-2-amino-2-deoxy-d-glucose [GlcNAcGlcN], the structure of which was determined by FABMS and NMR analyses. This study offers a novel method for enzymatic N-acetylation of amino sugars, and especially with chitobiose as substrate, a selectively N-acetylated product, GlcNAcGlcN, can be synthesized.