Appl Environ Microbiol, March 1998, p. 890-895, Vol. 64, No. 3
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
-D-Glucosaminidase from a Cellulolytic Fungus,
Trichoderma reesei PC-3-7
Department of Bioengineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-21, Japan
Received 17 July 1997/Accepted 23 December 1997
Chitosan-degrading activities induced by glucosamine (GlcN) or
N-acetylglucosamine (GlcNAc) were found in a culture
filtrate of Trichoderma reesei PC-3-7. One of the
chitosan-degrading enzymes was purified to homogeneity by precipitation
with ammonium sulfate followed by anion-exchange and
hydrophobic-interaction chromatographies. The enzyme was monomeric, and
its molecular mass was 93 kDa. The optimum pH and temperature of the
enzyme were 4.0 and 50°C, respectively. The activity was stable in
the pH range 6.0 to 9.0 and at a temperature below 50°C. Reaction
product analysis from the viscosimetric assay and thin-layer
chromatography and 1H nuclear magnetic resonance
spectroscopy clearly indicated that the enzyme was an exo-type
chitosanase, exo-
-D-glucosaminidase, that releases GlcN
from the nonreducing end of the chitosan chain. 1H nuclear
magnetic resonance spectroscopy also showed that the exo-
-D-glucosaminidase produced a
-form of GlcN,
demonstrating that the enzyme is a retaining glycanase. Time-dependent
liberation of the reducing sugar from partially acetylated chitosan
with exo-
-D-glucosaminidase and the partially purified
exo-
-D-N-acetylglucosaminidase from T. reesei PC-3-7 suggested that the
exo-
-D-glucosaminidase cleaves the glycosidic link of
either GlcN-
(1
4)-GlcN or GlcN-
(1
4)-GlcNAc.
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