抄録
The hydrolytic products of a chitinase purified from Nocardia orientalis were examined on reduced (GlcNAc)n(n = 2-6). The rate of hydrolysis on reduced (GlcNAc)4-6 increased with increasing chain-length of N-acetylglucosamine residues, but the enzyme did not act on reduced (GlcNAc)2 or reduced (GlcNAc)3. Based on the analysis of the frequency distribution of bond cleavage on PNP-(GlcNAc)n(n = 2-5) in the initial hydrolysis, the enzyme was shown to release predominantly (GlcNAc)2 from the nonreducing end of each substrate. The enzyme, which is essentially a hydrolase, also catalyzed a transglycosylation reaction in an excess of (GlcNAc)4 as an initial substrate. In this case, the addition of ammonium sulfate to the reaction system resulted in a significant increase in (GlcNAc)6 production. The yield of the hexasaccharide was about 34% of the chitinase-catalyzed net decrease of (GlcN Ac)4. The rate of the transglycosylation in the presence of ammonium sulfate greatly depended on the salt concentration, the temperature, and the substrate concentration.
