Abstract
Partial acid hydrolysis of chitin in mineral acid led to chitin-oligosaccharides of G1cNAc2-G1cNAc5 in quantitative yield, but it gives only low yields of G1cNAc5 and G1cNAc7 . So we tried to improve such higher oligosaccharides of the hexamer and heptamer. A chitinase from Nocardia orientalis could be used for the synthesis of G1cNAc6 and G1cNAc7 from G1cNAc4 and G1cNAc5 as the initial substrates, respectively. Sugar-elongation reaction from G1cNAc2 as an initial substrate to G1cNAc6 and G1cNAc7 was also efficiently induced through lysozyme catalysis. In these enzymatic reactions, the addition of ammonium sulfate to the reaction system resulted in a significant increase in the hexamer and heptamer productions . Furthermore, p-nitrophenyl penta-N acetyl-β-chitopentaoside (PNP-G1cNAc5), which is a substrate for a lysozyme assay, was synthesized by two techniques, enzymatically and chemically. On the other hand, enzymatic hydrolysis of chitosan by a chitosanase from Bacillus R-4 afforded a more convenient way of preparing chitosan-oligosaccharides (GlcN2-G1cN6) than the method using acid hydrolysis. Utilization of these oligosaccharides has also been studied. Chitin-oligosaccharides may be of use as food materials in sweetness and growth factors of intestinal bacteria. A new colonmetric assay method of lysozyme using PNP-G1cNAc5 as a substrate was very useful for routine microgram assay of lysozyme in pharmaceutical preparations and biological materials. The chromogenic trisaccharide analogue PNP-G1cNAc2 proved to be an excellent substrate for assaying bacterial chitinases.
