View source for Xylose

{{Short description|Sugar}}
{{redirect|Wood sugar|the related sugar alcohol|Xylitol}}
{{chembox
| Verifiedfields = changed
| Watchedfields  = changed
| verifiedrevid  = 458276050
| Name           = {{sm|d}}-Xylose
| ImageFileL1    = Xylose.svg
| ImageClassL1   = skin-invert 
| ImageNameL1    = D-Xylopyranose
| ImageFileR1    = Xylofuranose.png
| ImageClassR1   = skin-invert 
| ImageSizeR1    = 130px
| ImageNameR1    = Xylofuranose
| ImageFile2     = D-Xylose.svg
| ImageClass2    = skin-invert 
| ImageSize2     = 180px
| ImageName2     = Xylose chair
| ImageFile3     = Xylose linear.png
| ImageClass3    = skin-invert 
| ImageSize3     = 180px
| ImageName3     = Xylose linear
| IUPACName      = {{sm|d}}-Xylose
| OtherNames     = (+)-Xylose<br/>Wood sugar
| SystematicName = {{sm|d}}-''xylo''-Pentose<ref>{{Cite web | title=Appendix | url=https://iupac.qmul.ac.uk/2carb/app.html | access-date=2025-08-17 | website=iupac.qmul.ac.uk}}</ref>
| Section1       = {{Chembox Identifiers
| CASNo = 58-86-6
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo1 = 609-06-3
| CASNo1_Comment = ({{sm|l}}-isomer)
| CASNo1_Ref = {{cascite|correct|ESIS}}
| CASNo2 = 41247-05-6
| CASNo2_Comment = (racemate)
| CASNo2_Ref = {{cascite|correct|ESIS}}
| EC_number = 200-400-7 <!-- 210-174-1 for L-isomer, 255-277-2 for racemate -->
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = A1TA934AKO
| UNII1_Ref = {{fdacite|correct|FDA}}
| UNII1 = A4JW0V2MYA
| UNII1_Comment = ({{sm|l}}-isomer)
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 502135
| PubChem = 135191
| ChemSpiderID_Ref = {{chemspidercite|changed|chemspider}}
| ChemSpiderID = 119104
| SMILES = C1[C@H]([C@@H]([C@H](C(O1)O)O)O)O
| InChI = 1/C5H10O5/c6-2-1-10-5(9)4(8)3(2)7/h2-9H,1H2/t2-,3+,4-,5?/m1/s1
| InChIKey = SRBFZHDQGSBBOR-IOVATXLUBL
| StdInChI_Ref = {{stdinchicite|changed|chemspider}}
| StdInChI = 1S/C5H10O5/c6-2-1-10-5(9)4(8)3(2)7/h2-9H,1H2/t2-,3+,4-,5?/m1/s1
| StdInChIKey_Ref = {{stdinchicite|changed|chemspider}}
| StdInChIKey = SRBFZHDQGSBBOR-IOVATXLUSA-N
  }}
| Section2       = {{Chembox Properties
| Properties_ref =<ref>{{Merck11th|9995}}.</ref><ref>{{RubberBible62nd|page=C-574}}.</ref>
| Appearance = monoclinic needles or prisms, colourless
| Formula = {{chem|C|5|H|10|O|5}}
| Density = 1.525 g/cm<sup>3</sup> (20&nbsp;°C)
| MolarMass = 150.13 g/mol
| MeltingPtC = 144 to 145
| MeltingPt_notes = 
| SpecRotation = +22.5° ({{chem|C|H|Cl|3}})
| MagSus = −84.80·10<sup>−6</sup> cm<sup>3</sup>/mol
  }}
| Section7       = {{Chembox Hazards
| NFPA-H = 1
| NFPA-F = 1
| NFPA-R = 0
| FlashPt =
  }}
| Section8       = {{Chembox Related
| OtherFunction = [[Arabinose]]<br/>[[Ribose]]<br/>[[Lyxose]]
| OtherFunction_label = [[Pentose|aldopentoses]]
| OtherCompounds = [[Xylulose]]
  }}
}}

'''Xylose''' ({{abbr|cf.|compare with}} {{langx|grc|ξύλον}}, {{Transliteration|grc|xylon}}, "wood") is a common [[monosaccharide]], i.e. a simple sugar. Xylose is classified as [[aldopentose]] type, which means that it contains five [[carbon]] atoms and includes an [[aldehyde]] [[functional group]], at least in its open-chain form.  It is abundant in biomass, and is one of the most abundant sugars in nature.<ref>{{cite journal |last1=Thorsheim |first1=Karin |last2=Siegbahn |first2=Anna |last3=Johnsson |first3=Richard E. |last4=Stålbrand |first4=Henrik |last5=Manner |first5=Sophie |last6=Widmalm |first6=Göran |last7=Ellervik |first7=Ulf |title=Chemistry of xylopyranosides |journal=Carbohydrate Research |date=2015 |volume=418 |pages=65–88 |doi=10.1016/j.carres.2015.10.004 |pmid=26580709 |url=http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-125648 }}</ref>  It is a white, water-soluble solid.

==Structure==
The [[Open chain compound|acyclic]] form of xylose has [[chemical formula]] {{chem|HOCH|2|(CH(OH))|3C|H|O}}.  Cyclic [[hemiacetal]] isomers are more prevalent in solution. These cyclic isomers include the [[pyranose]]s feature six-membered {{chem2|C5O}} rings, and the [[furanose]]s, which feature five-membered {{chem|C|4|O}} rings (with a pendant {{chem|CH|2|OH}} group).  Each of these rings is subject to further isomerism, depending on the relative orientation of the anomeric hydroxy group.

The [[dextrorotation and levorotation|dextrorotary]] form, {{sm|d}}-xylose, is the one that usually occurs [[endogeny (biology)|endogenously]] in [[life|living things]]. A levorotary form, {{sm|l}}-xylose, can be [[organic synthesis|synthesized]].

==Occurrence==
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 [[embryo]]s of most edible plants. It was first isolated from wood by Finnish scientist, Koch, in 1881,<ref>{{cite book |editor-first=C.S. |editor-last=Hudson |editor2-first=S.M. |editor2-last=Cantor |title=Advances in Carbohydrate Chemistry |publisher=Elsevier |date=2014 |orig-date=1950 |volume=5 |isbn=9780080562643 |pages=278 |url=https://books.google.com/books?id=rUapoxXf-v4C}}</ref> but first became commercially viable, with a price close to [[sucrose]], in 1930.<ref>{{cite journal |first1=Mabel M. |last1=Miller |first2=Howard B. |last2=Lewis |title=Pentose Metabolism: I. The Rate of Absorption of d-Xylose and the Formation of Glycogen in the Organism of the White Rat after Oral Administration of d-Xylose |journal=Journal of Biological Chemistry |volume=98 |issue=1 |pages=133–140 |date=1932 |doi=10.1016/S0021-9258(18)76145-0 |doi-access=free }}</ref>

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]] [[polysaccharide]]s such as [[heparan sulfate]] and [[chondroitin sulfate]].<ref>{{citation | last1 = Buskas | first2 = Sampat | last2 = Ingale | first3 = Geert-Jan | last3 = Boons | title = Glycopeptides as versatile tool for glycobiology | journal = Glycobiology | volume = 16 | issue = 8 | pages = 113R–36R | year = 2006 | doi = 10.1093/glycob/cwj125 | pmid = 16675547 | first1 = Therese| doi-access = free }}</ref>

Xylose is also found in some species of Chrysolinina beetles, including ''Chrysolina coerulans''. They have [[cardiac glycosides]] (including xylose) in their defensive glands.<ref>{{cite book |first=E. David |last=Morgan |title=Biosynthesis in Insects |year=2004 |chapter=§ 7.3.1 Sterols in Insects |chapter-url={{google books|AbXid2E-17YC |page=112 |plainurl=yes}} |page=112 |publisher=Royal Society of Chemistry |isbn=9780854046911}}</ref>

== Applications ==

=== Chemicals ===
The acid-catalysed degradation of hemicellulose gives [[furfural]],<ref>{{OrgSynth | title = Furfural | volume = 1 | pages = 49 | year = 1921 | collvol = 1 | collvolpages = 280 |first= Roger |last=Adams |first2=V. |last2=Voorhees | prep = cv1p0280 |doi=10.15227/orgsyn.001.0049}}</ref><ref>{{cite journal|last=Gómez Millán |first=Gerardo|author2=Hellsten, Sanna|author3=King, Alistair W.T. |author4=Pokki, Juha-Pekka|author5=Llorca, Jordi|author6=Sixta, Herbert |title=A comparative study of water-immiscible organic solvents in the production of furfural from xylose and birch hydrolysate |journal=Journal of Industrial and Engineering Chemistry |date=25 April 2019|volume=72 |pages=354–363|doi=10.1016/j.jiec.2018.12.037|hdl=10138/307298|s2cid=104358224 |hdl-access=free}}</ref> a precursor to synthetic polymers and to [[tetrahydrofuran]].<ref>{{Ullmann|doi=10.1002/14356007.a12_119.pub2|chapter=Furfural and Derivatives|year=2007|last1=Hoydonckx|first1=H. E.|last2=Van Rhijn|first2=W. M.|last3=Van Rhijn|first3=W.|last4=De Vos|first4=D. E.|last5=Jacobs|first5=P. A.|isbn=978-3527306732}}
</ref>

=== Human consumption ===
Xylose is not a major human nutrient and is largely excreted by the kidneys.<ref>{{cite thesis |url=https://repository.up.ac.za/handle/2263/27501 |title=Physiological and microbiological studies of nectar xylose metabolism in the Namaqua rock mouse, ''Aethomys namaquensis'' (A. Smith, 1834)  |last=Johnson |first=S.A. |date=2007-08-24 |type=PhD |hdl=2263/27501}}</ref> Humans can obtain xylose only from their diet. An [[oxidoreductase]] pathway is present in [[eukaryotic microorganism]]s. Humans have enzymes called [[protein xylosyltransferase]]s ([[XYLT1]], [[XYLT2]]) which transfer xylose from UDP to a serine in the core protein of proteoglycans.

Xylose contains 2.4 calories per gram<ref>{{Cite patent|title=Method of producing xylose|gdate=1999-08-06 |number=US6239274B1 |country=US |url=https://patents.google.com/patent/US6239274B1/en}}</ref> (lower than glucose or sucrose, approx. 4 calories per gram).

=== Animal medicine ===

In animal medicine, [[D-Xylose absorption test|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.<ref>{{citation | url = https://medlineplus.gov/ency/article/003606.htm | title = D-xylose absorption | work = MedlinePlus | publisher = U.S. National Library of Medicine | date = July 2008 | access-date = 2009-09-06}}</ref>

High xylose intake on the order of approximately 100 g/kg of animal body weight is relatively well tolerated in pigs, and in a similar manner to results from human studies, a portion of the xylose ingested is excreted in urine unmodified.<ref>{{cite journal |vauthors=Schutte JB, de Jong J, Polziehn R, Verstegen MW |title=Nutritional implications of D-xylose in pigs |journal=Br J Nutr |volume=66 |issue=1 |pages=83–93 |date=July 1991 |pmid=1931909 |doi=10.1079/bjn19910012  |s2cid=27670020 |doi-access=free }}</ref>

=== Derivatives ===
[[Organic redox reaction|Reduction]] of xylose by catalytic [[hydrogenation]] produces the [[sugar substitute]] [[xylitol]].

==See also==
* ''[[Saccharophagus degradans]]''
* [[Xylonic acid]]
* [[Xylose metabolism]]

==References==
{{reflist}}

{{Carbohydrates}}

[[Category:Aldopentoses]]
[[Category:Dietary fiber]]
[[Category:Pyranoses]]
[[Category:Furanoses]]