title: Cellobiohydrolase B, a second exo-cellobiohydrolase from the cellulolytic bacterium Cellulomonas fimi.
abstract: The gene cbhB from the cellulolytic bacterium Cellulomonas fimi encodes a polypeptide of 1090 amino acids. Cellobiohydrolase B (CbhB) is 1037 amino acids long, with a calculated molecular mass of 109765 Da. The enzyme comprises five domains: an N-terminal catalytic domain of 643 amino acids, three fibronectin type III repeats of 97 amino acids each, and a C-terminal cellulose-binding domain of 104 amino acids. The catalytic domain belongs to family 48 of glycosyl hydrolases. CbhB has a very low activity on CM-cellulose. Viscometric analysis of CM-cellulose hydrolysis indicates that the enzyme is an exoglucanase. Cellobiose is the major product of hydrolysis of cellulose. In common with two other exoglycanases from C. fimi, CbhB has low but detectable endoglucanase activity. CbhB is the second exo-cellobiohydrolase found in C. fimi. Therefore, the cellulase system of C. fimi resembles those of fungi in comprising multiple endoglucanases and cellobiohydrolases.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, Vancouver, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Shen
authors.forename: N R
authors.initials: NR
authors.lastname: Gilkes
authors.forename: D G
authors.initials: DG
authors.lastname: Kilburn
authors.forename: R C
authors.initials: RC
authors.lastname: Miller
authors.forename: R A
authors.initials: RA
authors.lastname: Warren
mesh_terms: D000192:Actinomycetales / Q000201:enzymology*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D002482:Cellulose / Q000378:metabolism; D043366:Cellulose 1,4-beta-Cellobiosidase; D004274:DNA, Recombinant; D004926:Escherichia coli / Q000201:enzymology; D044643:Glucan 1,4-beta-Glucosidase; D006026:Glycoside Hydrolases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011994:Recombinant Proteins; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D001617:beta-Glucosidase
chemical_list: D004274:DNA, Recombinant; D011994:Recombinant Proteins; D002482:Cellulose; D006026:Glycoside Hydrolases; D001617:beta-Glucosidase; D044643:Glucan 1,4-beta-Glucosidase; D043366:Cellulose 1,4-beta-Cellobiosidase