Characterization of acetylated 4-O-methylglucuronoxylan isolated from aspen employing 1H and 13C NMR spectroscopy

Identification of a disaccharide side chain 2-O-α-D-galactopyranosyl-α-D-glucuronic acid inArabidopsisxylan

“…Since the proton resonances for GlcA and MeGlcA are overlapped in the 2D NMR spectrum, 27 it is not discernable whether the cross peak at H-1 of 5.42 ppm and H-2 of 3.7 ppm in the 2D TOCSY spectrum of Arabidopsis xylan contains both Gal-GlcA and Gal-MeGlcA, and thus it is designated as GalGlcA/MeGlcA (Fig. 1) The spectral positions of these proton cross peaks are in good agreement with those reported for acetylated xylans from E. globulus and aspen, 8,26 thus validating the reliability of the 2D TOCSY spectrum of Arabidopsis xylan.…”

“…2) corresponding to the resonances of Gal-MeGlcA disaccharide substituents, which is the same as that observed in E. globulus xylan. 26 Congruent with the 2D HSQC spectra of acetylated xylans from E. globulus and aspen, 8,26 other cross peaks of the 1 H and 13 C chemical shifts in the spectrum of Arabidopsis xylan correspond to GlcA/MeGlcA (the H-1/C-1 signals at 5.28/98.8 ppm), 2,3-di-O-acetylated xylosyl residues (H-3/C-3 at 5.17/74 ppm), 3-O-acetylated xylosyl residues substituted at O-2 with GlcA (H-3/C-3 at 5.08/75 ppm), 3-O-monoacetylated xylosyl residues (H-3/C-3 at 4.98/76.3 ppm and H-1/C-1 at 4.58/102.5 ppm), and non-acetylated internal xylosyl residues (H-1/C-1 at 4.42/104 and 4.48/103 ppm). Because xylooligomers released from xylanase digestion of acetylated xylan were used for NMR spectroscopy, cross peaks of H-1 and C-1 signals for reducing end α-xylose (H-1/C-1 at 5.18/93.2 ppm) and reducing end β-xylose (H-1/C-1 at 4.58/97.6 ppm) were prominent.…”

“…7 In addition to sugar substitutions, xylosyl residues in the xylan backbone may be acetylated at O-2 and/or O-3. 8 Since xylan is one of the factors contributing to the recalcitrance of cellulosic biomass to saccharification, 9 it is important to have a thorough understanding of xylan structure and of how genetic modification of xylan content and structure may alter lignocellulosic biomass recalcitrance in order to custom-design biomass composition tailored for biofuel production.…”

Understanding the structural and functional properties of carbohydrate esterases with a special focus on hemicellulose deacetylating acetyl xylan esterases

“…The sources of O -acetyl groups in primary and secondary cell walls of woody plants such as softwood and hardwood are observed to be as homogalacturonan, rhamnogalacturonan I, rhamnogalacturonan II (Pectin), xyloglucan, glucuronoarabinoxylan (type II primary cell walls of grasses), glucuronoxylan and glucomannans (Table 1). The degree of acetylation varies based on the type of tissue and plant species; it was reported that the degree of acetylation varied between 0.60 and 0.75 in glucuronoxylan of aspen wood and 0.3 and 0.4 in galactoglucomannan of spruce, aspen and birch wood (Teleman et al 2000, 2003). The acetyl groups were also found to migrate between the neighbouring free hydroxyl groups and the positions of which varies based on the species (Pauly 1999; Jacobs et al 2002; Mastihubová and Biely 2004) (Table 1).…”

Two Trichome Birefringence-Like Proteins Mediate Xylan Acetylation, Which Is Essential for Leaf Blight Resistance in Rice

“…The degrees of acetylation range from 0.3 to 0.6 acetate to Xyl ratio depending on the plant species Yuan et al, 2016c). Acetyl groups are attached to xylan xylopyranosyl residues at O-2 or O-3 and O-3 if O-2 contains other substituents, for example, GlcA/MeGlcA/Araf (Teleman et al, 2000). In addition to these two polymers, glucomannans, pectins, and lignin were also found to be O-acetylated at certain positions (Liners et al, 1994;Schols and Voragen, 1994;Lundqvist et al, 2002;del Río et al, 2008;Gille et al, 2011a).…”