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A family 10 Thermoascus aurantiacus xylanase utilizes arabinose decorations of xylan as significant substrate specificity determinants

Lookup NU author(s): Dr James Flint, Professor Rick Lewis, Emeritus Professor Harry Gilbert, Dr James Murray


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Xylan, which is a key component of the plant cell wall, consists of a backbone of β-1,4-linked xylose residues that are decorated with arabinofuranose, acetyl, 4-O-methyl d-glucuronic acid and ferulate. The backbone of xylan is hydrolysed by endo-β1,4-xylanases (xylanases); however, it is unclear whether the various side-chains of the polysaccharide are utilized by these enzymes as significant substrate specificity determinants. To address this question we have determined the crystal structure of a family 10 xylanase from Thermoascus aurantiacus, in complex with xylobiose containing an arabinofuranosyl-ferulate side-chain. We show that the distal glycone subsite of the enzyme makes extensive direct and indirect interactions with the arabinose side-chain, while the ferulate moiety is solvent-exposed. Consistent with the 3D structural data, the xylanase displays fourfold more activity against xylotriose in which the non-reducing moiety is linked to an arabinose side-chain, compared to the undecorated form of the oligosacchairde. These data indicate that the sugar decorations of xylans in the T. aurantiacus family 10 xylanase, rather than simply being accommodated, can be significant substrate specificity determinants. © 2005 Elsevier Ltd. All rights reserved.

Publication metadata

Author(s): Vardakou M, Flint JE, Christakopoulos P, Lewis RJ, Gilbert HJ, Murray JW

Publication type: Article

Publication status: Published

Journal: Journal of Molecular Biology

Year: 2005

Volume: 352

Issue: 5

Pages: 1060-1067

Print publication date: 07/10/2005

ISSN (print): 0022-2836

ISSN (electronic): 1089-8638

Publisher: Academic Press


DOI: 10.1016/j.jmb.2005.07.051

PubMed id: 16140328


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