title: Mode of action and substrate specificity of a purified exo-1,4-beta-D-glucosidase cloned from the cellulolytic bacterium Ruminococcus albus AR67.
abstract: A gene encoding exo-1,4-beta-D-glucosidase, from Ruminococcus albus AR67, was cloned in Escherichia coli, restriction mapped, and shown to be expressed from sequences within the insert that function as a promoter in E. coli. The cloned enzyme was located predominantly in the cytoplasm (40%) and attached to insoluble cell components (48%). After purification to homogeneity, the enzyme (Mr = 64,000, monomeric) was specific for substrates with beta-D-glucopyranosyl configuration and was inactive against alpha-glucosides, lactosides and xylosides. Km values of the enzyme decreased with increasing chain length (G2-G5). Glucose was the major product of hydrolysis from cellodextrins. Preference for longer chain cellodextrins is consistent with exo-1,4-beta-D-glucan glucohydrolase mode of action [E.C. 3.2.1.74].
authors.affiliation: Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, Australia.
authors.forename: C E
authors.initials: CE
authors.lastname: Ware
authors.forename: A H
authors.initials: AH
authors.lastname: Lachke
authors.forename: K
authors.initials: K
authors.lastname: Gregg
mesh_terms: D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003001:Cloning, Molecular; D004591:Electrophoresis, Polyacrylamide Gel; D015723:Gene Library; D044643:Glucan 1,4-beta-Glucosidase; D005959:Glucosidases / Q000378:metabolism*; D007700:Kinetics; D010459:Peptococcaceae / Q000201:enzymology* / Q000235:genetics; D010957:Plasmids; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D015183:Restriction Mapping; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D014462:Ultrafiltration; D001617:beta-Glucosidase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D005959:Glucosidases; D001617:beta-Glucosidase; D044643:Glucan 1,4-beta-Glucosidase