Planta

, 227:893

Anionic derivatives of xyloglucan function as acceptor but not donor substrates for xyloglucan endotransglucosylase activity

  • Takumi Takeda
  • Janice G. Miller
  • Stephen C. Fry
Original Article

Abstract

Tamarind xyloglucan was oxidised by reaction with sodium hypochlorite in the presence of 2,2,6,6-tetramethyl-1-piperidinyloxy free radical (TEMPO). Galactose residues and non-xylosylated glucose residues were thus converted into galacturonic and glucuronic acid residues, respectively, producing an anionic polysaccharide. Acid hydrolysis of oxidised xyloglucan yielded two aldobiouronic acids, deduced to be β-d-GalpA-(1→2)-d-Xyl and β-d-GlcpA-(1→4)-d-Glc. Anionic xyloglucan had a decreased ability to hydrogen-bond to cellulose and to complex with iodine. It was almost totally resistant to digestion by cellulase [endo-(1→4)-β-glucanase] and did not serve as a donor substrate for xyloglucan endotransglucosylase (XET) activity. Like several other anionic polysaccharides, it promoted XET activity when unmodified (non-ionic) xyloglucan was used as donor substrate. Anionic xyloglucan may mimic polyanions whose presence in the plant cell wall promotes the action of endogenous XTH proteins. NaOCl with TEMPO oxidised the heptasaccharide, XXXG, to form XXX-glucarate, which did serve as an acceptor substrate although at a rate approximately fourfold less than XXXG itself. Anionic derivatives of xyloglucan, acting as acceptor but not donor substrates, may be valuable tools for exploring the biological roles of XTHs in the integration versus the re-structuring of xyloglucan in the plant cell wall.

Keywords

Cell expansion Hemicellulose XET activity Transglycosylation Glucaric acid Xyloglucan oxidation 

Abbreviations

CMC

Carboxymethylcellulose

DP

Degree of polymerisation

GPC

Gel-permeation chromatography

HEC

Hydroxyethylcellulose

MLG

Mixed-linkage (1→3), (1→4)-β-d-glucan

PyAW

Pyridine/acetic acid/water (1:1:98, by vol., pH 4.7) containing 0.5% chlorobutanol

TEMPO

2,2,6,6-Tetramethyl-1-piperidinyloxy

TFA

Trifluoroacetic acid

TLC

Thin-layer chromatography

XEH

Xyloglucan endohydrolase (activity)

XET

Xyloglucan endotransglucosylase (activity)

XGO

Xyloglucan-derived oligosaccharide

XTH

Xyloglucan endotransglucosylase/hydrolase (protein)

XXXGol, XLLG, etc.

Oligosaccharides of xyloglucan (for abbreviated nomenclature see ref. Fry et al. 1993)

Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Takumi Takeda
    • 1
    • 2
  • Janice G. Miller
    • 1
  • Stephen C. Fry
    • 1
  1. 1.The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological SciencesThe University of EdinburghEdinburghUK
  2. 2.Iwate Biotechnology Research CenterIwateJapan

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