Document Detail


Mixed-linkage beta-glucan : xyloglucan endotransglucosylase, a novel wall-remodelling enzyme from Equisetum (horsetails) and charophytic algae.
MedLine Citation:
PMID:  18397375     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Mixed-linkage (1-->3,1-->4)-beta-d-glucan (MLG), a hemicellulose long thought to be confined to certain Poales, was recently also found in Equisetum; xyloglucan occurs in all land plants. We now report that Equisetum possesses MLG:xyloglucan endotransglucosylase (MXE), which is a unique enzyme that grafts MLG to xyloglucan oligosaccharides (e.g. the heptasaccharide XXXGol). MXE occurs in all Equisetum species tested (Equisetum arvense, Equisetum fluviatile, Equisetum hyemale, Equisetum scirpoides, Equisetum telmateia and Equisetum variegatum), sometimes exceeding xyloglucan endotransglucosylase (XET) activity. Charophytic algae, especially Coleochaete, also possess MXE, which may therefore have been a primordial feature of plant cell walls. However, MXE was negligible in XET-rich extracts from grasses, dicotyledons, ferns, Selaginella and bryophytes. This and the following four additional observations indicate that MXE activity is not the result of a conventional xyloglucan endotransglucosylase/hydrolase (XTH): (i) XET, but not MXE, activity correlates with the reaction rate on water-soluble cellulose acetate, hydroxyethylcellulose and carboxymethylcellulose, (ii) MXE and XET activities peak in old and young Equisetum stems, respectively, (iii) MXE has a higher affinity for XXXGol (K(m) approximately 4 microM) than any known XTH, (iv) MXE and XET activities differ in their oligosaccharide acceptor-substrate preferences. High-molecular-weight (M(r)) xyloglucan strongly competes with [(3)H]XXXGol as the acceptor-substrate of MXE, whereas MLG oligosaccharides are poor acceptor-substrates. Thus, MLG-to-xyloglucan grafting appears to be the favoured activity of MXE. In conclusion, Equisetum has evolved MLG plus MXE, potentially a unique cell wall remodelling mechanism. The prominence of MXE in mature stems suggests a strengthening/repairing role. We propose that cereals, which possess MLG but lack MXE, might be engineered to express this Equisetum enzyme, thereby enhancing the crop mechanical properties.
Authors:
Stephen C Fry; Kyle E Mohler; Bertram H W A Nesselrode; Lenka Franková
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-04-04
Journal Detail:
Title:  The Plant journal : for cell and molecular biology     Volume:  55     ISSN:  1365-313X     ISO Abbreviation:  Plant J.     Publication Date:  2008 Jul 
Date Detail:
Created Date:  2008-07-30     Completed Date:  2008-11-03     Revised Date:  2008-11-05    
Medline Journal Info:
Nlm Unique ID:  9207397     Medline TA:  Plant J     Country:  England    
Other Details:
Languages:  eng     Pagination:  240-52     Citation Subset:  IM    
Affiliation:
The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological Sciences, The University of Edinburgh, Edinburgh EH9 3JH, UK. s.fry@ed.ac.uk
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MeSH Terms
Descriptor/Qualifier:
Algae / enzymology*
Cellulose / analogs & derivatives,  metabolism
Equisetum / enzymology*
Glucans / metabolism*
Glycosyltransferases / metabolism*
Poaceae / enzymology
Substrate Specificity
Xylans / metabolism
Grant Support
ID/Acronym/Agency:
//Biotechnology and Biological Sciences Research Council
Chemical
Reg. No./Substance:
0/Glucans; 0/Xylans; 37294-28-3/xyloglucan; 9004-34-6/Cellulose; 9004-35-7/acetylcellulose; EC 2.4.-/Glycosyltransferases
Comments/Corrections
Erratum In:
Plant J. 2008 Sep;55(6):1062

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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