Reducing end groups in brich xylan and their alkaline degradation

Johansson, Mats H.; Samuelson, Olof

doi:10.1007/bf00356924

Cited by 127 publications

(64 citation statements)

References 6 publications

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“…MALDI-TOF MS of one of the fractions was enriched in an ion at m/z 761, consistent with the presence of an oligoglycosyl alditol. Such alditols are generated when the residue at the reducing end of the polysaccharide reacts with NaBH 4 , which is added to the alkaline extraction medium to avoid degradation by base-catalyzed peeling reactions (Johansson and Samuelson, 1977). To improve the separation of the xylooligosaccharides by reverse-phase HPLC, the reducing oligosaccharides were converted to their 2-aminobenzamide derivatives.…”

Section: )-D-xylp That Is Present At the Reducing End Of Arabidopsis Gxmentioning

confidence: 99%

“…The Xyl residues can also be substituted with arabinosyl and acetyl residues (Ebringerová and Heinze, 2000). Early work established that GX isolated from birch (Betula verrucosa) and spruce (Picea abies) wood contains the glycosyl sequence 4-b-D-Xylp-(1/4)-b-D-Xylp-(1/3)-a-L-Rhap-(1/2)-a-D-GalpA-(1/4)-D-Xylp at the reducing end (Shimizu et al, 1976;Johansson and Samuelson, 1977;Andersson et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

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Arabidopsis irregular xylem8andirregular xylem9: Implications for the Complexity of Glucuronoxylan Biosynthesis

et al. 2007

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Mutations of Arabidopsis thaliana IRREGULAR XYLEM8 (IRX8) and IRX9 were previously shown to cause a collapsed xylem phenotype and decreases in xylose and cellulose in cell walls. In this study, we characterized IRX8 and IRX9 and performed chemical and structural analyses of glucuronoxylan (GX) from irx8 and irx9 plants. IRX8 and IRX9 are expressed specifically in cells undergoing secondary wall thickening, and their encoded proteins are targeted to the Golgi, where GX is synthesized. 1 H-NMR spectroscopy showed that the reducing end of Arabidopsis GX contains the glycosyl sequence 4-b-D-, which was previously identified in birch (Betula verrucosa) and spruce (Picea abies) GX. This indicates that the reducing end structure of GXs is evolutionarily conserved in woody and herbaceous plants. This sequence is more abundant in irx9 GX than in the wild type, whereas irx8 and fragile fiber8 (fra8) plants are nearly devoid of it. The number of GX chains increased and the GX chain length decreased in irx9 plants. Conversely, the number of GX chains decreased and the chain length heterodispersity increased in irx8 and fra8 plants. Our results suggest that IRX9 is required for normal GX elongation and indicate roles for IRX8 and FRA8 in the synthesis of the glycosyl sequence at the GX reducing end.

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Section: )-D-xylp That Is Present At the Reducing End Of Arabidopsis Gxmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Arabidopsis irregular xylem8andirregular xylem9: Implications for the Complexity of Glucuronoxylan Biosynthesis

et al. 2007

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“…Dicot xylans are commonly substituted with α-(1→2)-linked glucuronosyl and 4-O-methyl glucuronosyl residues (1). Xylans in birch, spruce, and Arabidopsis have been found to contain the reducing end oligosaccharide (9)(10)(11) which, interestingly, has not been found in the xylan of grasses. Commelinid monocot xylans are unique from those of dicots and other monocots.…”

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confidence: 99%

XAX1 from glycosyltransferase family 61 mediates xylosyltransfer to rice xylan

Chiniquy

Sharma

Schultink

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

178

161

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Xylan is the second most abundant polysaccharide on Earth and represents an immense quantity of stored energy for biofuel production. Despite its importance, most of the enzymes that synthesize xylan have yet to be identified. Xylans have a backbone of β-1,4–linked xylose residues with substitutions that include α-(1→2)–linked glucuronosyl, 4- O -methyl glucuronosyl, and α-1,2- and α-1,3-arabinofuranosyl residues. The substitutions are structurally diverse and vary by taxonomy, with grass xylan representing a unique composition distinct from dicots and other monocots. To date, no enzyme has yet been identified that is specific to grass xylan synthesis. We identified a xylose-deficient loss-of-function rice mutant in Os02g22380, a putative glycosyltransferase in a grass-specific subfamily of family GT61. We designate the mutant xax1 for x ylosyl a rabinosyl substitution of x ylan 1. Enzymatic fingerprinting of xylan showed the specific absence in the mutant of a peak, which was isolated and determined by 1 H-NMR to be (β-1,4-Xyl) 4 with a β-Xyl p -(1→2)-α-Ara f -(1→3). Rice xax1 mutant plants are deficient in ferulic and coumaric acid, aromatic compounds known to be attached to arabinosyl residues in xylan substituted with xylosyl residues. The xax1 mutant plants exhibit an increased extractability of xylan and increased saccharification, probably reflecting a lower degree of diferulic cross-links. Activity assays with microsomes isolated from tobacco plants transiently expressing XAX1 demonstrated xylosyltransferase activity onto endogenous acceptors. Our results provide insight into grass xylan synthesis and how substitutions may be modified for increased saccharification for biofuel generation.

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“…2 The reducing end of the xylan backbone from gymnosperms and dicots also contains a distinct tetrasaccharide sequence, β-D-Xyl-(1→3)-α-l-Rha-(1→2)-α-D-GalA-(1→4)-D-Xyl. [3][4][5][6] Xylan from dicots is typically substituted with single residues of α-D-glucuronic acid (GlcA) and 4-O-methyl-α-Dglucuronic acid (MeGlcA) at O-2. Xylan from lignified tissues of grasses is substituted with α-L-arabinose (Ara) at O-3 in addition to the 2-O-linked GlcA and MeGlcA, and that from cereal grains is mainly substituted with Ara residues at O-2 and O-3.…”

mentioning

confidence: 99%