Xylose

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D-Xylose
D-Xylopyranose Xylofuranose
Xylose chair
Xylose linear
Identifiers
CAS number 58-86-6 YesY, 609-06-3 (L-isomer) YesY[ESIS], 41247-05-6 (racemate) YesY[ESIS]
PubChem 135191
ChemSpider 119104 N
UNII A1TA934AKO YesY
EC-number 200-400-7
ChEMBL CHEMBL502135 N
Jmol-3D images Image 1
Properties[1][2]
Molecular formula C5H10O5
Molar mass 150.13 g/mol
Appearance monoclinic needles or prisms, colourless
Density 1.525 g/cm3 (20 °C)
Melting point 144–145 °C
Chiral rotation [α]D +22.5° (CHCl3)
Hazards
NFPA 704
Flammability code 1: Must be pre-heated before ignition can occur. Flash point over 93 °C (200 °F). E.g., canola oil Health code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentine Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related aldopentoses Arabinose
Ribose
Lyxose
Related compounds Xylulose
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Xylose (cf. Greek ξύλον, xylon, "wood") is a sugar first isolated from wood, and named for it. Xylose is classified as a monosaccharide of the aldopentose type, which means that it contains five carbon atoms and includes a formyl functional group. It is derived from hemicellulose, one of the main constituents of biomass. Like most sugars, it can adopt several structures depending on conditions. With its free carbonyl group, it is a reducing sugar.

Structure[edit]

The acyclic form of xylose has chemical formula HOCH2(CH(OH))3CHO. The cyclic hemiacetal isomers are more prevalent in solution and are of two types: the pyranoses, which feature six-membered C5O rings, and the furanoses, which feature five-membered C4O rings (with a pendant CH2OH group). Each of these rings subject to further isomerism, depending on the relative orientation of the anomeric hydroxy group.

Occurrence[edit]

Xylose is the main building block for the hemicellulose xylan, which comprises about 30% of some plants (birch for example), far less in others (spruce and pine have about 9% xylan). Xylose is otherwise pervasive, being found in the embryos of most edible plants. It was first isolated from wood by Koch in 1881.

Xylose is also the first saccharide added to the serine or threonine in the proteoglycan type O-glycosylation, and, so, it is the first saccharide in biosynthetic pathways of most anionic polysaccharides such as heparan sulfate and chondroitin sulfate.[3]

Applications[edit]

Chemicals[edit]

The acid-catalysed degradation of hemicellulose gives furfural,[4] a specialty solvent in industry and a precursor to synthetic polymers.[5]

Human consumption[edit]

Xylose is metabolised by humans, though it is not a major human nutrient and largely excreted by the kidneys.[6] Humans must obtain xylose from their diet. An oxido-reductase pathway is present in eukaryotic microorganisms. Humans have an enzyme called xylosyltransferase, which transfers xylose from UDP to a serine in the core protein of proteoglycans.[citation needed]

Animal medicine[edit]

In animal medicine, xylose is used to test for malabsorption by administration in water to the patient after fasting. If xylose is detected in blood and/or urine within the next few hours, it has been absorbed by the intestines.[7] Reduction of xylose by catalytic hydrogenation produces the non-cariogenic sugar substitute xylitol.

Hydrogen production[edit]

In 2014 a low-temperature 50 °C (122 °F), atmospheric-pressure enzyme-driven process to convert xylose into hydrogen with nearly 100% of the theoretical yield was announced. The process employs 13 enzymes, including a novel polyphosphate xylulokinase (XK).[8][9]

See also[edit]

References[edit]

  1. ^ The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN 091191028X , 9995.
  2. ^ Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. C-574. ISBN 0-8493-0462-8. .
  3. ^ Buskas, Therese; Ingale, Sampat; Boons, Geert-Jan (2006), Glycopeptides as versatile tool for glycobiology, Glycobiology 16 (8): 113R–36R, doi:10.1093/glycob/cwj125, PMID 16675547 
  4. ^ Roger Adams and V. Voorhees (1921), Furfural, Org. Synth. 1: 49 ; Coll. Vol. 1: 280 
  5. ^ H. E. Hoydonckx, W. M. Van Rhijn, W. Van Rhijn, D. E. De Vos, P. A. Jacobs "Furfural and Derivatives" in Ullmann's Encyclopedia of Industrial Chemistry 2007, Wiley-VCH, Weinheim. doi:10.1002/14356007.a12_119.pub2
  6. ^ Johnson, S. A. (2006). "Thesis". 
  7. ^ D-xylose absorption, MedlinePlus (U.S. National Library of Medicine), July 2008, retrieved 2009-09-06 
  8. ^ "Virginia Tech team develops process for high-yield production of hydrogen from xylose under mild conditions". Green Car Congress. 2013-04-03. doi:10.1002/anie.201300766. Retrieved 2014-01-22. 
  9. ^ Martín Del Campo, J. S.; Rollin, J.; Myung, S.; Chun, Y.; Chandrayan, S.; Patiño, R.; Adams, M. W.; Zhang, Y. -H. P. (2013). "High-Yield Production of Dihydrogen from Xylose by Using a Synthetic Enzyme Cascade in a Cell-Free System". Angewandte Chemie International Edition 52 (17): 4587. doi:10.1002/anie.201300766.  edit