|Superclasses:||all carbohydrates → a carbohydrate → a glycan → a polysaccharide → hemicellulose|
Xylan is a general name given for polysaccharides composed of xylose residues. It is the principal type of hemicellulose in plant biomass representing the second most abundant polysaccharide in the biosphere after cellulose [Schadel10].
The most common form of xylan is a (1→4)-β-D-xylan, which is found in the cell walls of plants and some algae. Pure (1→4)-β-D-xylan is uncommon. In most cases it is decorated with additional sugars, in the form of arabinoxylan, glucuronoxylan, glucuronoarabinoxylan or arabinoglucuronoxylan.
The secondary hydroxyl groups on xylose carbons 2 and 3 can be substituted by a number of residues, the type and degree of substitution depending on xylan's botanical source. Arabinose and glucuronic acid are linked to the backbone by glycosidic bonds. Other substituents form ester bonds: acetate groups are bound directly to the backbone, while cinnamoyl (feruloyl and coumaroyl) residues are linked to the side chain arabinoses [Joseleau92].
Due to its heterogeneous structure, the biodegradation of xylan requires the concerted action of a complex set of enzymes [Gordillo06]. These enzymes are mainly extracellular and are secreted by numerous fungi and bacteria [Biely85]. The endoxylanases and β xylosidases hydrolyze the main chain; the former generating short chain oligosaccharides and the latter acting on these products to liberate xylose. The side chains are hydrolyzed by glycanases, α-glucuronidases, acetyl xylan esterases and feruloyl esterases [deVries01].
(1->3)-β-D-xylan is found only in cell walls of some red and green algae.
Reactions known to consume the compound:
Reactions known to produce the compound:
Carpita93: Carpita NC, Gibeaut DM (1993). "Structural models of primary cell walls in flowering plants: consistency of molecular structure with the physical properties of the walls during growth." Plant J 3(1);1-30. PMID: 8401598
Deniaud03: Deniaud E, Quemener B, Fleurence J, Lahaye M (2003). "Structural studies of the mix-linked beta-(1-->3)/beta-(1-->4)-D-xylans from the cell wall of Palmaria palmata (Rhodophyta)." Int J Biol Macromol 33(1-3);9-18. PMID: 14599578
Gordillo06: Gordillo F, Caputo V, Peirano A, Chavez R, Van Beeumen J, Vandenberghe I, Claeyssens M, Bull P, Ravanal MC, Eyzaguirre J (2006). "Penicillium purpurogenum produces a family 1 acetyl xylan esterase containing a carbohydrate-binding module: characterization of the protein and its gene." Mycol Res 110(Pt 10);1129-39. PMID: 17008082
Kiyohara06: Kiyohara M, Hama Y, Yamaguchi K, Ito M (2006). "Structure of beta-1,3-xylooligosaccharides generated from Caulerpa racemosa var. laete-virens beta-1,3-xylan by the action of beta-1,3-xylanase." J Biochem 140(3);369-73. PMID: 16891637
Lahaye03: Lahaye M, Rondeau-Mouro C, Deniaud E, Buleon A (2003). "Solid-state 13C NMR spectroscopy studies of xylans in the cell wall of Palmaria palmata (L. Kuntze, Rhodophyta)." Carbohydr Res 338(15);1559-69. PMID: 12860427
Polizeli05: Polizeli ML, Rizzatti AC, Monti R, Terenzi HF, Jorge JA, Amorim DS (2005). "Xylanases from fungi: properties and industrial applications." Appl Microbiol Biotechnol 67(5);577-91. PMID: 15944805
Schadel10: Schadel C, Richter A, Blochl A, Hoch G (2010). "Hemicellulose concentration and composition in plant cell walls under extreme carbon source-sink imbalances." Physiol Plant 139(3);241-55. PMID: 20113432
SchooneveldBerg99: Schooneveld-Bergmans, M.E. F., Dignum, M. J. W., Grabber, J. H.., Beldman, G., Voragen, A. G. J. (1999). "Studies on the oxidative cross-linking of feruloylated arabinoxylans from wheat flour and wheat bran." Carbohydrate Polymers 38:309-317.
Vignon98: Vignon, M. R., Gey, C. (1998). "Isolation, 1H and 13C NMR studies of (4-O-methyl-D-glucurono)-D-xylans from luffa fruit fibres, jute bast fibres and mucilage of quince tree seeds." Carbohydrate Research 307(1-2):107-111.
Yamagaki96: Yamagaki, T., Maeda, M., Kabazawa, K., Ishizuka, Y, Nakanishi, H. (1996). "Structures of Caulerpa cell wall microfibril xylan with detection of ?-1,3-xylooligosaccharides as revealed by matrix-assisted laser desorption ionization/time of flight/mass spectrometry." Biosci. Biotech. Biochem. 60, 1222-1228.
©2015 SRI International, 333 Ravenswood Avenue, Menlo Park, CA 94025-3493