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J. Bacteriol., Mar 1995, 1641-1644, Vol 177, No. 6
K Kruus, WK Wang, J Ching and JH Wu
The recombinant CelS (rCelS), the most abundant catalytic subunit of the
Clostridium thermocellum cellulosome, displayed typical exoglucanase
characteristics, including (i) a preference for amorphous or crystalline
cellulose over carboxymethyl cellulose, (ii) an inability to reduce the
viscosity of a carboxymethyl cellulose solution, and (iii) the production
of few bound reducing ends on the solid substrate. The hydrolysis products
from crystalline cellulose were cellobiose and cellotriose at a ratio of
5:1. The rCelS activity on amorphous cellulose was optimal at 70 degrees C
and at pH 5 to 6. Its thermostability was increased by Ca2+. Sulfhydryl
reagents had only a mild adverse effect on the rCelS activity.
Cellotetraose was the smallest oligosaccharide substrate for rCelS, and the
hydrolysis rate increased with the substrate chain length. Many of these
properties were consistent with those of the cellulosome, indicating a key
role for CelS.
Copyright © 1995, American Society for Microbiology
Exoglucanase activities of the recombinant Clostridium thermocellum CelS, a major cellulosome component
Department of Chemical Engineering, University of Rochester, New York 14627-0166.
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