Exoglucanase activities of the recombinant Clostridium thermocellum CelS, a major cellulosome component.
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.
Kruus
K
K
Department of Chemical Engineering, University of Rochester, New York 14627-0166.
Wang
W K
WK
Ching
J
J
Wu
J H
JH
D001483:Base Sequence; D002480:Cellulase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*; D003013:Clostridium / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D003912:Dextrins / Q000378:metabolism; D043326:Glucan 1,3-beta-Glucosidase; D006868:Hydrolysis; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013379:Substrate Specificity; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014783:Viscosity; D001617:beta-Glucosidase / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
D003912:Dextrins; D009097:Multienzyme Complexes; D011994:Recombinant Proteins; D013439:Sulfhydryl Reagents; D002482:Cellulose; C068994:cellodextrin; C071223:endoglucanase Ss; D001617:beta-Glucosidase; D002480:Cellulase; D043326:Glucan 1,3-beta-Glucosidase