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Journal of Bacteriology, September 1999, p. 5461-5466, Vol. 181, No. 17
Osaka University of Pharmaceutical Sciences,
4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan
Received 19 April 1999/Accepted 21 June 1999
We purified from the culture supernatant of Alteromonas
sp. strain O-7 and characterized a transglycosylating enzyme which synthesized
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Molecular Analysis of the Gene Encoding a Novel
Transglycosylative Enzyme from Alteromonas sp. Strain O-7
and Its Physiological Role in the Chitinolytic System
-(1
6)-(GlcNAc)2,
2-acetamido-6-O-(2-acetamido-2-deoxy-
-D-glucopyranosyl)-2-deoxyglucopyranose from
-(1
4)-(GlcNAc)2. The gene encoding a novel
transglycosylating enzyme was cloned into Escherichia coli,
and its nucleotide sequence was determined. The molecular mass of the
deduced amino acid sequence of the mature protein was determined to be
99,560 Da which corresponds very closely with the molecular mass of the
cloned enzyme determined by sodium dodecyl sulfate-polyacrylamide gel
electrophoresis. The molecular mass of the cloned enzyme was much
larger than that of enzyme (70 kDa) purified from the supernatant of
this strain. These results suggest that the native enzyme was the
result of partial proteolysis occurring in the N-terminal region. The
enzyme showed significant sequence homology with several bacterial
-N-acetylhexosaminidases which belong to family 20 glycosyl hydrolases. However, this novel enzyme differs from all
reported
-N-acetylhexosaminidases in its substrate
specificity. To clarify the role of the enzyme in the chitinolytic
system of the strain, the effect of
-(1
6)-(GlcNAc)2 on the induction of chitinase was investigated.
-(1
6)-(GlcNAc)2 induced a level of production of
chitinase similar to that induced by the medium containing chitin. On
the other hand, GlcNAc, (GlcNAc)2, and
(GlcNAc)3 conversely repressed the production of chitinase to below the basal level of chitinase activity produced constitutively in medium without a carbon source.
*
Corresponding author. Mailing address: Osaka University
of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan. Phone and fax: (81-726) 90-1057. E-mail:
tsujibo{at}oysun01.oups.ac.jp.
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