Plant Physiol. Biochem. 39 (2001) 927−932
© 2001 Éditions scientifiques et médicales Elsevier SAS. All rights reserved
S0981942801013134/FLA
Release of complexed xyloglucan endotransglycosylase (XET)
from plant cell walls by a transglycosylation reaction
with xyloglucan-derived oligosaccharides
Zdena Sulová, Richard Baran, Vladimír Farkaš*
Institute of Chemistry, Slovak Academy of Sciences, Dúbravská cesta 9, 84238 Bratislava, Slovakia
Received 30 March 2001; accepted 17 June 2001
Abstract – Incubation of isolated NaCl-washed cell walls from epicotyls of pea (Pisum sativum) and nasturtium (Tropaeolum
majus) with solutions of various oligosaccharides released among others the cell wall marker enzyme xyloglucan endotransglycosylase (XET, EC 2.4.1.207). The greatest release of XET occurred upon incubation of the cell walls with xyloglucanderived oligosaccharides (XGOS, DP 7-9). Concomitantly, reduced radioactive nonasaccharide [3H]-XLLGol (Gal2.Xyl3.Glc3.[13
H]-glucitol) was incorporated into the cell walls. Subsequent hydrolysis of the radioactively labelled cell walls with
Trichoderma cellulase liberated XGOS-alditols, DP 7-9 as the sole radioactive products indicating that [3H]-XLLGol was
incorporated into the cell wall xyloglucan by transglycosylation, as an entity. Oligosaccharides of cello-, chito- and/or
oligoglucurono-series were much less effective than XGOS but a substantial liberation of XET and other proteins from plant cell
walls could be achieved by the nucleophile 0.1 M imidazole. The specific release of the cell wall-associated XET activity by
incubation with xyloglucan-derived oligosaccharides and the simultaneous incorporation of the tritiated xyloglucan nonasaccharide en bloc into the cell walls indicates that XET is present in the cell walls in form of a competent glycosyl-enzyme complex
which decomposes by transglycosylation of its glycan moiety to added xyloglucan-oligosaccharide acceptors. This finding
suggests a new concept for the regulation of activity of cell wall-associated glycanases/transglycosylases: they exist in plant cell
walls in a transiently latent state as covalent glycosyl-enzyme complexes and are active only when suitable glycosyl acceptors
become available. © 2001 Éditions scientifiques et médicales Elsevier SAS
cell walls / nasturtium / Pisum sativum / transglycosylation / Tropaeolum majus / XET / xyloglucan / xyloglucanendotransglycosylase
XET, xyloglucan endotransglycosylase (EC 2.4.1.207) / XG, xyloglucan / XGOS, xyloglucan-derived oligosaccharides
1. INTRODUCTION
Xyloglucan (XG) is the principal hemicellulosic
component of primary cell walls of dicotyledonous
and non-graminaceous monocotyledonous plants. Its
molecule consists of β-(1,4)-linked polyglucosyl main
chain highly branched by substitutions at C-6 by
α-xylosyl units. To C-2 of some of the xylosyl units,
terminal galactosyl units are attached by β-glycosidic
linkage. Some galactosyls are substituted at C-2 by
α-L-fucosyl residues. Owing to its strong affinity to
associate with cellulose by means of hydrogen-bonding,
XG is thought to play an important role in maintaining
*Correspondence and reprints: fax +421 2 5941 0222.
E-mail address: [email protected] (V. Farkaš).
cell wall integrity by cross-linking individual cellulose
microfibrils in the primary plant cell walls [7, 11]. The
enzyme mediating the reversible formation of xyloglucan cross-links and catalysing molecular grafting of
newly arriving XG molecules into the cell wall structure is xyloglucan endotransglycosylase (XET, EC
2.4.1.207; [8, 25]), or endo-xyloglucan transglycosylase (EXT, [16, 18]). The mechanism of XET-catalysed
reaction appears to be the one typical for retaining
glycanases or transglycosylases, i.e. it involves the
double inversion of anomericity of the glycosidic bond
with formation of a covalent glycosyl-enzyme intermediate, where the glycosyl is linked by an ester bond
at C-1 to the base-forming carboxyl group in the
molecule of the enzyme [14]. The XG-XET reaction
intermediate is relatively stable against hydrolysis but
readily decomposes by transglycosylation of its xylo
928
Z. Sulová et al. / Plant Physiol. Biochem. 39 (2001) 927–932
glucan moiety to a suitable xyloglucan-derived oligosaccharide acceptor [23]. The latter property has
recently been exploited in purification of XET from
different plant sources [20, 21].
Experimental data indicate that a substantial portion
of XET is located in primary plant cell walls, in close
proximity to its substrate xyloglucan [12, 26]. XET has
been detected as soluble in the apoplastic and symplastic fluids [2, 17] and also ionically bound to the
cell walls from where it can be extracted with buffers
of high pH and/or high ionic strength [1, 12, 24]. A
portion of active XET appears to be covalently bound
to the cell wall [2] but the nature of the covalent
binding of XET to the cell wall is not known. Based on
the previous indirect evidence that the enzyme is able
to form in vitro a relatively stable covalent intermediate with its substrate xyloglucan [23], it could be
assumed that it could also exist in plant cell walls
conserved in the form of a competent glycosyl-enzyme
intermediate. Our present finding that the active enzyme
can be released from the cell walls by incubation with
XGOS whereby added radioactive XGOS become
incorporated into the cell walls supports this hypothesis.
2. RESULTS AND DISCUSSION
2.1. Release of XET from the cell walls
by transglycosylation
Plant cell walls grow by expansion under internal
turgor pressure while loosening intramolecular ties and
incorporating newly synthesized building blocks supplied from inside the cell into the pre-existing structure
[4]. It can be anticipated that enzymes involved in
loosening and modification of the cell walls are
located primarily in the cell walls, in close association
with their respective substrates.
To prove the existence of a covalent intermediary
XET-xyloglucan complex in the growing cell walls,
isolated cell walls from pea and/or nasturtium epicotyls were thoroughly washed with 1 M NaCl to remove
loosely bound proteins. The NaCl extraction and
washing removed between 82 and 86 % of the total
measurable XET activity. The washed cell walls were
incubated with the buffer and with buffered solutions
of various effectors and the XET activity released into
the supernatant was determined.
From all oligosaccharides tested, xyloglucan-derived
XGOS were the most effective in releasing the XET
activity into the solution. Incubation of the washed cell
walls with XGOS (1 mg·mL–1) caused a time-dependent
Figure 1. Time-course of XET solubilization from nasturtium epicotyl cell walls during incubation with 1 mg·mL–1 XGOS in 50 mM
citrate-phosphate buffer (pH 5.5) (A), (XET activity values solubilized
by the buffer alone were subtracted) and incorporation of
[3H]-XLLGol into the cell walls in a parallel experiment (B).
Conditions were as described in Methods. (Open symbols), native cell
walls; (filled symbols), heat-denatured cell walls. The points in the
graphs are average values from two parallel determinations.
release of proteins and XET activity into the supernatant (figure 1A). The release of XET was paralleled by
incorporation of radioactive [3H]-XLLGol into the
insoluble fraction (figure 1B). Some release of XET
and cell wall-associated proteins was also detected
during incubation of the cell walls with buffered
solutions of cello- (DP 1-7), chito- (DP 1-5) and/or
oligogalacturono- (DP 1-12) oligosaccharides (figure 2). There was, however, considerable difference in
specific activity of XET in the individual types of
extracts. As shown in figure 2, considerable XET
activity was also released from the cell walls by
incubating them with 0.1 M imidazole buffered to
pH 5.5. The results obtained with cell walls from both
nasturtium and pea were very similar, although the
absolute values of XET activities differed.
The effectivity of imidazole to solubilize XET from
the cell walls could be explained in several ways. First,
imidazole is a nucleophile and as such it could attack
and decompose the putative ester bond between the
xyloglucan and XET in the XG-XET complex [23].
Z. Sulová et al. / Plant Physiol. Biochem. 39 (2001) 927–932
Figure 2. Effectiveness of solubilization of XET from NaCl-washed
cell walls by 1 h incubation with: 1, buffer (pH 5.5); 2, 0.1 M
imidazole (pH 5.5); 3, XGOS (1 mg·mL–1, DP 7-9); 4, cellooligosaccharides; 5 chitooligosaccharides (DP 1-4, 1 mg·mL–1); 6, pectic acid
fragments (DP 1-8, 1 mg·mL–1), all in the buffer as in figure 1. Empty
bars correspond to cell walls from nasturtium epicotyls, filled bars to
cell walls from pea epicotyls.
Second, imidazole has been described as a reversible,
active site-directed inhibitor of glycanases and glycosidases ([6] and references cited therein). It could
therefore react with the active site-located carboxyls
on the enzyme thereby preventing the formation of the
glycosyl-enzyme complex. Still another possibility is
that imidazole could compete with histidine residues
in complexing metal ions that might be involved in the
attachment of XET to xyloglucan.
2.2. Incorporation of [1-3H]-XLLGol
into the cell walls
Besides the liberation of the enzyme from the
XG-XET complex, the expected result of transglycosylation would be the incorporation of the oligosaccharide acting as the glycosyl acceptor into the xyloglucan fraction of the cell walls. Indeed, the release of
XET from the cell walls was paralleled by gradual
incorporation of radioactivity from XG-derived nonasaccharide [1-3H]-XLLGol into the cell wall sediment
(figure 1B). Practically no incorporation of radioactivity was observed into the cell walls that had been
inactivated by boiling for 5 min.
In order to prove that the radioactive XG-nonasaccharide was incorporated into xyloglucan, the labelled
cell walls were treated with Trichoderma cellulase.
Gel-chromatographic resolution of the cellulase digest
also revealed besides the original [3H]-nonasaccharide
the presence of radioactive octasaccharide and heptasaccharide (figure 3). The occurrence of the lower
929
Figure 3. Gel-permeation chromatography on Biogel P2 column of
cellulase digest from nasturtium epicotyl cell walls containing incorporated [3H]-XLLGol. Arrows indicate eluting positions of XGOS
standards (9), nonasaccharide, XLLG; (8), octasaccharide, XXLG;
and (7), heptasaccharide, XXXG; Glc, glucose; V0, void volume.
homologous oligosaccharides in the hydrolysate can
be explained by degalactosylation of the original
[3H]-nonasaccharide by β-galactosidase whose presence in the cell walls was detected (not shown). The
finding of radioactive XGOS as the sole radioactive
products of cellulase digestion of labelled cell walls
confirms that [1-3H]-XLLGol was incorporated en
bloc into the cell walls by transglycosylation and
linked to xyloglucan component by a β-1,4-glycosidic
bond.
2.3. SDS-PAGE analysis of proteins extracted
from the cell walls
Figure 4 shows SDS-PAGE of proteins solubilized
from the NaCl-washed nasturtium cell walls by incubation with 0.1 M imidazole (pH 5.5), and buffered
solutions of 1 mg·mL–1 XGOS and 1 mg·mL–1 cellooligosaccharides respectively. The presence of multiple bands in the individual lanes on the gel indicates
the complexity of the protein composition of the cell
walls and possible interactions between the individual
proteins in the walls. At first glance, qualitative differences between the profiles of proteins released by the
buffer, XGOS, cellooligosaccharides and/or imidazole
were small. There were prominent, as yet unidentified
protein bands at 66, 42, 27, 23, 18 and 16 kDa in all
three lanes. However, no distinct band between 31 and
34 kDa expected to correspond to XET from nasturtium epicotyls [19] could be seen in the imidazole
and/or XGOS lanes where the specific activity of XET
was the highest (cf. figure 2). Our attempts to detect
released epicotyl XET after SDS-PAGE by western
930
Z. Sulová et al. / Plant Physiol. Biochem. 39 (2001) 927–932
tions would then depend solely on the availability of
the respective substrates acting as glycosyl acceptors,
be it water for hydrolysis or another saccharide for
transglycosylation. Such mechanism would explain
the ‘growth promoting’ effect of XGOS as demonstrated in pea epicotyl segments [15] and pea shoots
[5]. Since the cell wall is a highly hydrated structure,
the availability of free water molecules is greatly
reduced by their binding to hemicellulosic wall components. On the other hand, the saccharide acceptors
are supplied de novo and synthesized by the cell or can
be formed by hydrolysis of the existing wall polysaccharides.
Figure 4. Silver-stained SDS-PAGE of proteins eluted from nasturtium epicotyl cell walls. 1, 0.1 M imidazole (pH 5.5); 2, XGOS,
1 mg·mL–1; 3, cellooligosaccharides, 1 mg·mL–1.
3. CONCLUSION
blotting using an antibody raised against nasturtiumseed XET [23] were, possibly due to a low degree of
homology between the two enzymes [19], unsuccessful.
The results presented here show that significant
portions of XET, and possibly also other cell wallrelated proteins (glycanases/transglycosylases), exist
in the walls associated to their respective substrates,
presumably in the form of stable intermediate glycosylenzyme complexes which decompose by transglycosylation of their glycosyl moieties to suitable acceptors. Since the cell wall loosening or modifying
enzymes are in fact extracellular, the conventional
types of controls of enzyme activity (e.g. by chemical
modification, degradation, synthesis, inhibitors or allosteric effectors) have probably only limited effectiveness. An alternative mechanism must exist regulating
their activity so as to prevent them from weakening the
cell wall at times of reduced growth. It is possible that
the hydrolases/transglycosylases are kept at bay by
forming stable intermediary complexes with their
respective substrates. The continuation of their reac-
Our results show that a small but significant portion
of XET activity (∼15 %) exists firmly (presumably
covalently) bonded to plant cell walls in the form of a
transient glycosyl-enzyme complex. The complex could
be decomposed by transglycosylation of the glycan
moiety to XGOS acting as glycosyl acceptors. The
transglycosylation reaction was accompanied by timedependent liberation of XET and incorporation of
radioactive XGOS into the cell walls. It could be
envisaged that the formation of stable enzyme-substrate
intermediate complexes represents a new type of
regulation of glycanases/transglycosylases participating in the process of plant cell wall formation and
modification. At times of reduced growth, the supply
of potential glycosyl acceptors would be slowed down
and the cell wall transglycosylases would become
‘frozen’ in a latent state as covalent glycosyl-enzyme
complexes. Whenever their respective glycosyl acceptors become available, transglycosylation would ensue
and the enzymes would be released from the complexes free to attack other substrate molecules (figure 5).
Figure 5. Scheme depicting the mechanism of XET release from the cell walls by transglycosylation of glycan moiety from XG-XET complexes
to XGOS. CM, cellulose microfibril; XG, xyloglucan; XGOS*, exogenously added radioactive xyloglucan-derived oligosaccharides.
Z. Sulová et al. / Plant Physiol. Biochem. 39 (2001) 927–932
4. METHODS
4.1. Oligosaccharides
Xyloglucan-derived oligosaccharides (XGOS, DP
7-9, a mixture of XXXG, XLXG, XXLG and XLLG,
average Mr 1 250) were prepared by partial hydrolysis
of tamarind seed xyloglucan by Trichoderma cellulase
as previously described [22]. The nomenclature of
xyloglucan-derived oligosaccharides used in this work
is the one suggested by Fry et al. [10]. Radioactive
alditol
[1-3H]-XLLGol,
specific
radioactivity
17 MBq·µmol–1 was prepared by reduction of
XG-derived nonasaccharide XLLG with NaB3H4 in a
conventional way. The product was further purified by
TLC on Silicagel 60 plates, 0.2-mm thickness (Merck)
using the solvent system n-propanol/methanol/water
(2/1/1, v/v/v). The zone corresponding to the radioactive nonasaccharide was located by autoradiography,
scraped out and eluted from the TLC plate by 20 %
(v/v) ethanol. A mixture of cellooligosaccharides (DP
1-7) was prepared by acetolysis of cotton cellulose
[27]. Chitooligosaccharides (DP 1-6) were a gift from
Dr E. Machová and fragments of oligogalacturonic
acid (DP 1-7) were kindly provided by Dr A. Malovíková, both from our Institute.
4.2. Plant material and the isolation of cell walls
Seeds of nasturtium (Tropaeolum majus L., cv.
Goldshine orange) were germinated in wet perlite
under day-night regime at 22–24 °C for 6–8 d and
their epicotyls were collected. Seeds of pea (Pisum
sativum L., cv. Tyrkys), were germinated in darkness
at 22 °C for 6 d. In some experiments, the collected
epicotyls were stored at –20 °C for several days before
further use. All subsequent operations were performed
at 4 °C. The epicotyls (5–11 g wet wt.) were homogenized for 5 min in a kitchen blender at maximum
speed for 3 × 1 min with three volumes (related to wet
wt. of biomass) of 1 M NaCl in 50 mM citratephosphate buffer (pH 5.5) and the homogenates were
filtered through Miracloth. The cell wall debris retained
on the cloth were suspended in the buffered 1 M NaCl
and centrifuged at 1 500 × g for 20 min and the sediment was washed several times with the same solution
until the supernatant had no absorbancy at 280 nm.
931
with occasional stirring. Aliquots were taken from the
suspensions at time intervals, centrifuged at 15 000 × g
for 15 min and the supernatants were dialysed against
the buffer and analysed for protein and XET activity.
After 1 h, the residual suspensions were centrifuged
and the supernatants were dialysed against three changes
of the buffer at 4 °C for 16–20 h and concentrated to a
small volume by evaporation in a Speedvac.
4.4. Kinetics of [1-3H]-XLLGol incorporation
into the cell walls
The incubation mixture contained 0.5 g (wet wt.)
washed cell walls suspended in 1 mL 50 mM citratephosphate buffer (pH 5.5) and 43 kBq carrier-free
[1-3H]-XLLGol. The mixture was incubated at 25 °C
and 100-µL aliquots were taken in duplicates at time
intervals, centrifuged and washed three times with
cold water. The washed sediments were then suspended in 200 µL water and 600 µL scintillation liquid
Optiphase (LKB) were added and shaken to make a
firm gel and their radioactivity was determined in a
liquid scintillation counter (Rackbeta 1214, LKBWallac). In a scaled-up experiment, 1 g (wet wt.)
NaCl-washed cell walls from nasturtium epicotyls
were incubated with 214 kBq [3H]-XXLGol in 2 mL
buffer. The suspension was incubated at 25 °C for
30 min with gentle shaking and after being washed
three times with ice-cold water, the labelled cell walls
were digested with 0.1 % crude dialysed Trichoderma
cellulase and 0.02 % NaN3 in 1.5 mL 50 mM citratephosphate buffer (pH 5.5) overnight at room temperature. The cellulase digest was chromatographed on
BioGel P2 column (0.7 × 90 cm) eluted with 0.02 %
NaN3. Fractions (1 mL) were collected and their
radioactivity was determined in a liquid scintillation
counter.
4.5. Analytical methods
4.3. Cell wall extractions
XET activity was assayed radiometrically according
to Fry et al. [9]. The isocratic HPLC chromatography
of XGOS was performed on a TSK Gel Amide (Tosoh)
column 4.5 mm i.d. × 250 mm, using 65 % (v/v) acetonitrile in water as the eluent. Proteins were determined
by the method of Bradford [3] using cytochrome c as
the standard. SDS-PAGE was performed according to
Laemmli [13] using separating gel of T = 10 % and
C = 2.6 %.
The NaCl-washed cell walls were distributed into
test tubes in 1 g (wet wt.) aliquots and incubated at
30 °C with 5 mL 50 mM citrate-phosphate buffer
(pH 5.5) containing different effectors, as indicated
Acknowledgments. This work was supported by
grant No. 2/7137/20 from the Slovak Grant Agency for
Science (VEGA).
932
Z. Sulová et al. / Plant Physiol. Biochem. 39 (2001) 927–932
REFERENCES
[1] Antosiewitz D., Purugganan M.M., Polisensky D.,
Braam J., Cellular localization of arabidopsis xyloglucan endotransglycosylase-related proteins during development and after wind stimulation, Plant Physiol. 115
(1997) 1319–1328.
[2] Barrachina C., Lorences E., Xyloglucan endotransglycosylase activity in pine hypocotyls. Intracellular localization and relationship with endogenous growth,
Physiol. Plant. 102 (1998) 55–60.
[3] Bradford M.M., A rapid and sensitive method for
quantitation of microgram quantities of protein utilizing the principle of protein-dye binding, Anal. Biochem. 72 (1976) 248–254.
[4] Cosgrove D.J., Enzymes and other agents that enhance
cell wall extensibility, Annu. Rev. Plant Physiol. Plant
Mol. Biol. 50 (1999) 391–417.
[5] Cutillas-Iturralde A., Lorences E.P., Effect of xyloglucan oligosaccharides on growth, viscoelastic properties
and long-term extension of pea shoots, Plant Physiol.
113 (1997) 103–109.
[6] Field R.A., Haines A.H., Chrystal E.J.T.,
Luszniak M.C., Histidines, histamines and imidazoles
as glycosidase inhibitors, Biochem. J. 274 (1991)
885–889.
[7] Fry S.C., The structure and functions of xyloglucan,
J. Exp. Bot. 40 (1989) 1–11.
[8] Fry S.C., Polysaccharide-modifying enzymes in the
plant cell wall, Annu. Rev. Plant Physiol. Plant Mol.
Biol. 46 (1995) 497–520.
[9] Fry S.C., Smith R.C., Renwick K.I., Martin D.J.,
Hodge S.K., Mathews K.J., Xyloglucan endotransglycosylase, a new wall-loosening enzyme activity from
plants, Biochem. J. 282 (1992) 821–828.
[10] Fry S.C., York W.S., Albersheim P., Darvill A.,
Hayashi T., Joseleau J.P., Kato Y., Lorences E.P.,
Maclachlan G.A., McNeil M., Mort A.J., Reid J.S.G.,
Seitz H.U., Selvendran R.R., Voragen A.G.J.,
White A.R., An unambiguous nomenclature for
xyloglucan-derived oligosaccharides, Physiol. Plant.
89 (1993) 1–3.
[11] Hayashi T., Xyloglucans in the primary cell wall,
Annu. Rev. Plant Physiol. Plant Mol. Biol. 40 (1989)
139–168.
[12] Ito H., Nishitani K., Visualization of EXGT-mediated
molecular grafting activity by means of a fluorescentlabeled xyloglucan oligomer, Plant Cell Physiol. 40
(1999) 1172–1176.
[13] Laemmli E.K., Cleavage of structural proteins during
the assembly of the head of bacteriophage T4, Nature
227 (1970) 680–685.
[14] Ly H.H., Withers S., Mutagenesis of glycosidases,
Annu. Rev. Biochem. 68 (1999) 487–522.
[15] McDougall G.J., Fry S.C., Xyloglucan oligosaccharides promote growth and activate cellulase: evidence
[16]
[17]
[18]
[19]
[20]
[21]
[22]
[23]
[24]
[25]
[26]
[27]
for a role of cellulase in cell-wall expansion, Plant
Physiol. 93 (1990) 1042–1048.
Nishitani K., Construction and restructuring of the
cellulose-xyloglucan framework in the apoplast as
mediated by the xyloglucan-related protein family - a
hypothetical scheme, J. Plant Res. 111 (1998) 159–166.
Nishitani K., Tominaga R., In vitro molecular weight
increase in xyloglucans by an apoplastic enzyme
preparation from epicotyls of Vigna angularis, Physiol.
Plant. 82 (1991) 490–497.
Nishitani K., Tominaga R., Endo-xyloglucan transferase, a novel class of glycosyltransferase that catalyzes transfer of a segment of xyloglucan molecule to
another xyloglucan molecule, J. Biol. Chem. 267
(1992) 21058–21064.
Rose J.C., Brummel D.A., Bennett A.B., Two divergent endotransglycosylases exhibit mutually exclusive
patterns of expression in nasturtium, Plant Physiol. 110
(1996) 493–499.
Steele N.M., Fry S.C., Purification of xyloglucan
endotransglycosylases (XETs): a generally applicable
and simple method based on reversible formation of an
enzyme-substrate complex, Biochem. J. 340 (1999)
207–211.
Sulová Z., Farkaš V., Purification of xyloglucan endotransglycosylase based on affinity sorption of the active
glycosyl-enzyme intermediate complex to cellulose,
Prot. Expr. Purif. 16 (1999) 231–235.
Sulová Z., Lednická M., Farkaš V., A colorimetric
assay for xyloglucan endotransglycosylase from germinating seeds, Anal. Biochem. 229 (1995) 80–85.
Sulová Z., Takáčová M., Steele N., Fry S.C., Farkaš V.,
Xyloglucan endotransglycosylase: evidence for the
existence of a relatively stable glycosyl-enzyme intermediate, Biochem. J. 330 (1998) 1475–1480.
Tabuchi A., Kamisaka S., Hoson T., Purification of
xyloglucan hydrolase/endotransglycosylase from cell
walls of azuki bean hypocotyls, Plant Cell Physiol. 38
(1997) 653–658.
Thompson J.E., Smith R.C., Fry S.C., Xyloglucan
undergoes interpolymeric transglycosylation during
binding to the plant cell wall in vivo: evidence from
13 3
C/ H dual labelling and isopycnic centrifugation in
caesium trifluoroacetate, Biochem. J. 327 (1997)
699–708.
Vissenberg K., Martinez-Vilchez I.M., Verbelen J.P.,
Miller J.G., Fry S.C., In vivo colocalization of xyloglucan endotransglycosylase activity and its donor
substrate in the elongation zone of Arabidopsis roots,
Plant Cell 12 (2000) 1229–1237.
Wolfrom M.L., Thompson A., Acetolysis, in: Whistler R.L., Green J.W., BeMiller J.N., Wolfrom M.L.
(Eds.), Methods in Carbohydrate Chemistry, vol. III,
Cellulose, Academic Press Inc., New York and London, 1963, pp. 143–150.