Carbohydrate esterases of family 2 are 6-O-deacetylases

Topakas, Evangelos; Kyriakopoulos, Sarantos; Biely, Peter; Hirsch, Ján; Vafiadi, Christina; Christakopoulos, Paul

doi:10.1016/j.febslet.2009.11.095

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Volume 584, Issue 3 , Pages 543-548, 5 February 2010

Carbohydrate esterases of family 2 are 6-O-deacetylases

Edited by Stuart Ferguson

Evangelos Topakas
- BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, 15700 Athens, Greece
- Corresponding author. Fax: +30 210 7723163.
Sarantos Kyriakopoulos
- BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, 15700 Athens, Greece
Peter Biely
- Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 38 Bratislava, Slovak Republic
Ján Hirsch
- Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 38 Bratislava, Slovak Republic
Christina Vafiadi
- BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, 15700 Athens, Greece
Paul Christakopoulos
- BIOtechMASS Unit, Biotechnology Laboratory, School of Chemical Engineering, National Technical University of Athens, 5 Iroon Polytechniou Str, Zografou Campus, 15700 Athens, Greece

Received 2 October 2009; received in revised form 29 November 2009; accepted 30 November 2009. published online 07 December 2009.

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.

Keywords: Acetyl esterase, Transesterification, CE-2 family, 6-O-Deacetylase, Cellvibrio japonicus, Clostridium thermocellum

Abbreviations: CE, carbohydrate esterases, AcE, acetyl esterase, AcXE, acetylxylan esterase, 4-NPh–OH, 4-nitrophenol