Structural insight into the ligand specificity of a thermostable family 51 arabinofuranosidase, Araf 51, from Clostridium thermocellum

Taylor, Edward J. and Smith, Nicola L and Turkenburg, Johan P. and D'Souza, Simone and Gilbert, Harry J. and Davies, Gideon J. (2005) Structural insight into the ligand specificity of a thermostable family 51 arabinofuranosidase, Araf 51, from Clostridium thermocellum. Biochemical Journal, 395 . pp. 31-37. ISSN 0264-6021

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Official URL: http://dx.doi.org/10.1042/BJ20051780

Abstract

The digestion of the plant cellwall requires the concerted action of a diverse repertoire of enzyme activities. An important component of these hydrolase consortia are arabinofuranosidases, which release L-arabinofuranose moieties from a range of plant structural polysaccharides. The anaerobic bacterium Clostridium thermocellum, a highly efficient plant cell wall degrader, possesses a single α-L-arabinofuranosidase (EC 3.2.1.55), CtAraf51A, located
in GH51 (glycoside hydrolase family 51). The crystal structure of the enzyme has been solved in native form and in ‘Michaelis’ complexes with bothα-1,5-linkedarabinotriose andα-1,3 arabinoxylobiose, both forming a hexamer in the asymmetric unit. Kinetic studies reveal that CtAraf 51A, in contrast with well-characterized GH51 enzymes including the Cellvibrio japonicus enzyme [Beylot, McKie, Voragen, Doeswijk-Voragen and Gilbert (2001) Biochem. J. 358, 607–614], catalyses the hydrolysis of α-1,5- linked arabino-oligosaccharides and the α-1,3 arabinosyl side chain decorations of xylan with equal efficiency. The paucity
of direct hydrogen bonds with the aglycone moiety and the flexible conformation adopted by Trp178, which stacks against the sugar at the +1 subsite, provide a structural explanation for the plasticity in substrate specificity displayed by the clostridial arabinofuranosidase.
Taylor, E. J., Smith, N. L., Turkenburg, J. P., D'Souza, S., Gilbert, H. J. & Davies, G. J

Item Type:Article
Additional Information:The digestion of the plant cellwall requires the concerted action of a diverse repertoire of enzyme activities. An important component of these hydrolase consortia are arabinofuranosidases, which release L-arabinofuranose moieties from a range of plant structural polysaccharides. The anaerobic bacterium Clostridium thermocellum, a highly efficient plant cell wall degrader, possesses a single α-L-arabinofuranosidase (EC 3.2.1.55), CtAraf51A, located in GH51 (glycoside hydrolase family 51). The crystal structure of the enzyme has been solved in native form and in ‘Michaelis’ complexes with bothα-1,5-linkedarabinotriose andα-1,3 arabinoxylobiose, both forming a hexamer in the asymmetric unit. Kinetic studies reveal that CtAraf 51A, in contrast with well-characterized GH51 enzymes including the Cellvibrio japonicus enzyme [Beylot, McKie, Voragen, Doeswijk-Voragen and Gilbert (2001) Biochem. J. 358, 607–614], catalyses the hydrolysis of α-1,5- linked arabino-oligosaccharides and the α-1,3 arabinosyl side chain decorations of xylan with equal efficiency. The paucity of direct hydrogen bonds with the aglycone moiety and the flexible conformation adopted by Trp178, which stacks against the sugar at the +1 subsite, provide a structural explanation for the plasticity in substrate specificity displayed by the clostridial arabinofuranosidase. Taylor, E. J., Smith, N. L., Turkenburg, J. P., D'Souza, S., Gilbert, H. J. & Davies, G. J
Keywords:arabinan, arabinofuranosidase, Clostridium thermocellum
Subjects:C Biological Sciences > C700 Molecular Biology, Biophysics and Biochemistry
Divisions:College of Science > School of Life Sciences
ID Code:6164
Deposited By: Edward Taylor
Deposited On:18 Sep 2012 11:32
Last Modified:13 Mar 2013 09:13

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