Structure and activity of two metal ion-dependent acetylxylan esterases involved in plant cell wall degradation reveals a close similarity to peptidoglycan deacetylases

Taylor, Edward J. and Gloster, Tracey M. and Turkenburg, Johan P. and Vincent, Florence and Brzozowski, A. Marek and Dupont, Claude and Shareck, Francois and Centeno, Maria S. J. and Prates, Jose A. M. and Puchart, Vladimir and Ferreira, Luis M. A. and Fontes, Carlos M. G. A. and Biely, Peter and Davies, Gideon J. (2006) Structure and activity of two metal ion-dependent acetylxylan esterases involved in plant cell wall degradation reveals a close similarity to peptidoglycan deacetylases. The Journal of Biological Chemistry, 281 (16). pp. 10968-10975. ISSN 0021-9258

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Official URL: http://dx.doi.org/10.1074/jbc.M513066200

Abstract

The enzymatic degradation of plant cell wall xylan requires the concerted action of a diverse enzymatic syndicate. Among these enzymes are xylan esterases, which hydrolyze the O-acetyl substituents, primarily at the O-2 position of the xylan backbone. All acetylxylan esterase structures described previously display a alpha/beta hydrolase fold with a "Ser-His-Asp" catalytic triad. Here we report the structures of two distinct acetylxylan esterases, those from Streptomyces lividans and Clostridium thermocellum, in native and complex forms, with x-ray data to between 1.6 and 1.0 A resolution. We show, using a novel linked assay system with PNP-2-O-acetylxyloside and a beta-xylosidase, that the enzymes are sugar-specific and metal ion-dependent and possess a single metal center with a chemical preference for Co2+. Asp and His side chains complete the catalytic machinery. Different metal ion preferences for the two enzymes may reflect the surprising diversity with which the metal ion coordinates residues and ligands in the active center environment of the S. lividans and C. thermocellum enzymes. These "CE4" esterases involved in plant cell wall degradation are shown to be closely related to the de-N-acetylases involved in chitin and peptidoglycan degradation (Blair, D. E., Schuettelkopf, A. W., MacRae, J. I., and Aalten, D. M. (2005) Proc. Natl. Acad. Sci. U. S. A., 102, 15429-15434), which form the NodB deacetylase "superfamily."

Item Type:Article
Additional Information:The enzymatic degradation of plant cell wall xylan requires the concerted action of a diverse enzymatic syndicate. Among these enzymes are xylan esterases, which hydrolyze the O-acetyl substituents, primarily at the O-2 position of the xylan backbone. All acetylxylan esterase structures described previously display a alpha/beta hydrolase fold with a "Ser-His-Asp" catalytic triad. Here we report the structures of two distinct acetylxylan esterases, those from Streptomyces lividans and Clostridium thermocellum, in native and complex forms, with x-ray data to between 1.6 and 1.0 A resolution. We show, using a novel linked assay system with PNP-2-O-acetylxyloside and a beta-xylosidase, that the enzymes are sugar-specific and metal ion-dependent and possess a single metal center with a chemical preference for Co2+. Asp and His side chains complete the catalytic machinery. Different metal ion preferences for the two enzymes may reflect the surprising diversity with which the metal ion coordinates residues and ligands in the active center environment of the S. lividans and C. thermocellum enzymes. These "CE4" esterases involved in plant cell wall degradation are shown to be closely related to the de-N-acetylases involved in chitin and peptidoglycan degradation (Blair, D. E., Schuettelkopf, A. W., MacRae, J. I., and Aalten, D. M. (2005) Proc. Natl. Acad. Sci. U. S. A., 102, 15429-15434), which form the NodB deacetylase "superfamily."
Keywords:acetylxylan esterase, plant cell wall degradation
Subjects:C Biological Sciences > C700 Molecular Biology, Biophysics and Biochemistry
Divisions:College of Science > School of Life Sciences
ID Code:6163
Deposited By: Edward Taylor
Deposited On:18 Sep 2012 11:43
Last Modified:13 Mar 2013 09:13

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