title: Cloning and expression of Clostridium thermocellum genes coding for thermostable exoglucanases (cellobiohydrolases) in Escherichia coli cells.
abstract: By special screening approach two independent Cl. thermocellum genes directing the synthesis of thermostable glucanases with an exo-mode of action have been isolated from pUC19-based gene bank in E. coli TG1. The genes are located on 3.4 and 11.3 kb DNA fragments showing no homology. E. coli-derived exoglucanases, presumably, cellobiohydrolases, are able to cleave lichenan, carboxymethyl cellulose, xylan and p-nitrophenyl derivatives of cellobioside and lactoside. Cellobiose is the main degradation product of carboxymethyl cellulose, treated with the identified exoglucanases. With p-nitrophenil-beta-D-cellobioside as substrate the enzymes had a pH optimum around 6.5 and a temperature optimum at 65 degrees C. The identified and expressed enzymes differ from all other Cl. thermocellum proteins known to date.
authors.affiliation: Institute of Molecular Genetics, USSR Academy of Sciences, Moscow.
authors.forename: K
authors.initials: K
authors.lastname: Tuka
authors.forename: V V
authors.initials: VV
authors.lastname: Zverlov
authors.forename: B K
authors.initials: BK
authors.lastname: Bumazkin
authors.forename: G A
authors.initials: GA
authors.lastname: Velikodvorskaya
authors.lastname: Strongin AYa
mesh_terms: D043366:Cellulose 1,4-beta-Cellobiosidase; D003001:Cloning, Molecular; D003013:Clostridium / Q000201:enzymology / Q000235:genetics*; D015723:Gene Library; D005798:Genes, Bacterial; D043326:Glucan 1,3-beta-Glucosidase; D005959:Glucosidases / Q000235:genetics*; D006026:Glycoside Hydrolases / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D011994:Recombinant Proteins / Q000378:metabolism; D015183:Restriction Mapping; D013379:Substrate Specificity; D013696:Temperature; D001617:beta-Glucosidase / Q000235:genetics* / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D005959:Glucosidases; D006026:Glycoside Hydrolases; D001617:beta-Glucosidase; D043326:Glucan 1,3-beta-Glucosidase; D043366:Cellulose 1,4-beta-Cellobiosidase