title: Carbohydrate esterases of family 2 are 6-O-deacetylases.
abstract: Three acetyl esterases (AcEs) from the saprophytic bacteria Cellvibrio japonicus and Clostridium thermocellum, members of the carbohydrate esterase (CE) family 2, were tested for their activity against a series of model substrates including partially acetylated gluco-, manno- and xylopyranosides. All three enzymes showed a strong preference for deacetylation of the 6-position in aldohexoses. This regioselectivity is different from that of typical acetylxylan esterases (AcXEs). In aqueous medium saturated with vinyl acetate, the CE-2 enzymes catalyzed transacetylation to the same position, i.e., to the primary hydroxyl group of mono- and disaccharides. Xylose and xylooligosaccharides did not serve as acetyl group acceptors, therefore the CE-2 enzymes appear to be 6-O-deacetylases.
authors.affiliation: Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, Athens, Greece. vtopakas@central.ntua.gr
authors.forename: Evangelos
authors.initials: E
authors.lastname: Topakas
authors.forename: Sarantos
authors.initials: S
authors.lastname: Kyriakopoulos
authors.forename: Peter
authors.initials: P
authors.lastname: Biely
authors.forename: Ján
authors.initials: J
authors.lastname: Hirsch
authors.forename: Christina
authors.initials: C
authors.lastname: Vafiadi
authors.forename: Paul
authors.initials: P
authors.lastname: Christakopoulos
mesh_terms: D000107:Acetylation; D000115:Acetylesterase / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002241:Carbohydrates / Q000737:chemistry; D020633:Cellvibrio / Q000201:enzymology; D048013:Acetivibrio thermocellus / Q000201:enzymology; D006601:Hexoses / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009005:Monosaccharides / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity; D014994:Xylose / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002241:Carbohydrates; D006601:Hexoses; D009005:Monosaccharides; D014994:Xylose; D000115:Acetylesterase; C081851:acetylxylan esterase