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Appl Environ Microbiol, May 1998, p. 1644-1649, Vol. 64, No. 5
Centre de Bioingénierie Gilbert Durand,
UMR CNRS 5504, LA INRA, INSA, Complexe Scientifique de Rangueil,
31077 Toulouse cedex, France
Received 6 November 1997/Accepted 20 February 1998
Dextransucrase (DSR-S) from Leuconostoc mesenteroides
NRRL B-512F is a glucosyltransferase that catalyzes synthesis of
soluble dextran from sucrose. In the presence of efficient acceptor
molecules, such as maltose, the reaction pathway is shifted toward
glucooligosaccharide synthesis. Like glucosyltransferases from oral
streptococci, DSR-S possesses a C-terminal glucan-binding domain
composed of a series of tandem repeats. In order to determine the role
of the C-terminal region of DSR-S in dextran or oligosaccharide
synthesis, four DSR-S genes with deletions at the 3' end were
constructed. The results showed that the C-terminal region modulated
the initial velocity of dextran synthesis but that the
Km for sucrose, the optimum pH, and the
activation energy were all unaffected by the deletions. The C-terminal
domain modulated the rate of oligosaccharide synthesis whatever
acceptor molecule was used (a good acceptor molecule such as maltose or
a poor acceptor molecule such as fructose). The C-terminal domain
seemed to play no role in the catalytic process in dextran and
oligosaccharide synthesis. In fact, it seems that the role of the
C-terminal domain of DSR-S may be to facilitate the translation of
dextran and oligosaccharides from the catalytic site.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Effect of Leuconostoc mesenteroides NRRL B-512F
Dextransucrase Carboxy-Terminal Deletions on Dextran and
Oligosaccharide Synthesis
*
Corresponding author. Mailing address: Centre de
Bioingénierie Gilbert Durand, INSA, Complexe Scientifique de
Rangueil, 31077 Toulouse cedex, France. Phone: 33-5-61-55-94-46. Fax:
33-5-61-55-94-00. E-mail: willemot{at}insa-tlse.fr.
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