Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/59304
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Type: Journal article
Title: Barley xyloglucan xyloglucosyl transferases bind xyloglucan-derived oligosaccharides in their acceptor-binding regions in multiple conformational states
Author: Vaaj-Kolstad, G.
Farkas, V.
Fincher, G.
Hrmova, M.
Citation: Archives of Biochemistry and Biophysics, 2010; 496(1):61-68
Publisher: Academic Press Inc
Issue Date: 2010
ISSN: 0003-9861
1096-0384
Statement of
Responsibility: 
Gustav Vaaje-Kolstad, Vladimír Farkaš, Geoffrey B. Fincher, Maria Hrmova
Abstract: Three barley xyloglucan endotransglycosylases (HvXETs), known as xyloglucan xyloglucosyl transferases (EC 2.4.1.207), were subjected to kinetic and computational docking studies. The k(cat) x K(m)(-1) values with the reduced [3H]-labelled XXXG, XXLG/XLXG and XLLG acceptor substrates were 0.02 x 10(-2), 0.1 x 10(-2) and 3.2 x 10(-2) s(-1) microM(-1), while the K(m) constants were 10.6, 8.6 and 5.3 mM, obtained for HvXET3, HvXET4 and HvXET6, respectively. Docking of XLLG in acceptor-binding regions revealed that at least two conformational states were likely to participate in all isoforms. The assessments of kinetic and computational data indicated that the disposition of aromatic residues at the entrance to the active sites and the flexibility of proximal COOH-terminal loops could orient acceptors more or less favourably during binding, thus leading to tighter or weaker K(m) constants. The data suggested that binding of acceptors in HvXETs is guided by contributions from the conserved residues in the active sites and by the of neighbouring loops.
Keywords: Automated docking; Family GH16 glycoside hydrolases; Molecular modelling; Plant cell walls; Transglycosylation; Xyloglucan-derived oligosaccharides
Rights: Crown copyright © 2010 Published by Elsevier Inc.
RMID: 0020095217
DOI: 10.1016/j.abb.2010.01.011
Appears in Collections:Agriculture, Food and Wine publications

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