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Issue 24, 2007
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Glycosynthase activity of hybrid aspen xyloglucan endo-transglycosylase PttXET16-34 nucleophile mutants

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Abstract

Glycosynthases are active-site mutants of glycoside hydrolases that catalyse glycosyl transfer using suitable activated donor substrates without competing product hydrolysis (S. M. Hancock, M. D. Vaughan and S. G. Withers, Curr. Opin. Chem. Biol., 2006, 10, 509–519). Site-directed mutagenesis of the catalytic nucleophile, Glu-85, of a Populus tremula x tremuloides xyloglucan endo-transglycosylase (PttXET16-34, EC 2.4.1.207) into alanine, glycine, and serine yielded enzymes with glycosynthase activity. Product analysis indicated that PttXET16-34 E85A in particular was able to catalyse regio- and stereospecific homo- and hetero-condensations of α-xylogluco-oligosaccharyl fluoride donors XXXGαF and XLLGαF to produce xyloglucans with regular sidechain substitution patterns. This substrate promiscuity contrasts that of the Humicola insolens Cel7B E197A glycosynthase, which was not able to polymerise the di-galactosylated substrate XLLGαF. The production of the PttXET16-34 E85A xyloglucosynthase thus expands the repertoire of glycosynthases to include those capable of synthesising structurally homogenenous xyloglucans for applications.

Graphical abstract: Glycosynthase activity of hybrid aspen xyloglucan endo-transglycosylase PttXET16-34 nucleophile mutants

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Publication details

The article was received on 20 Sep 2007, accepted on 03 Oct 2007 and first published on 22 Oct 2007


Article type: Paper
DOI: 10.1039/B714570E
Citation: Org. Biomol. Chem., 2007,5, 3971-3978
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    Glycosynthase activity of hybrid aspen xyloglucan endo-transglycosylase PttXET16-34 nucleophile mutants

    K. Piens, A. Henriksson, F. Gullfot, M. Lopez, R. Fauré, F. M. Ibatullin, T. T. Teeri, H. Driguez and H. Brumer, Org. Biomol. Chem., 2007, 5, 3971
    DOI: 10.1039/B714570E

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