Xylose

From Wikipedia, the free encyclopedia
(Redirected from L-xylose)
Jump to navigation Jump to search

Template:Short description Script error: No such module "redirect hatnote". <templatestyles src="Chembox/styles.css"/>

Template:Chembox image cellTemplate:Chembox image cellTemplate:Chembox AllOtherNamesTemplate:Chembox headerbarTemplate:Chembox IndexlistTemplate:Chembox JmolTemplate:Chembox ChEMBLTemplate:Chembox ECHATemplate:Chembox E numberTemplate:Chembox IUPHAR ligandTemplate:Chembox UNIITemplate:Chembox CompToxTemplate:Chembox headerbarTemplate:Chembox HazardsTemplate:Chembox headerbarTemplate:Chembox Datapage checkTemplate:Yesno
<templatestyles src="smallcaps/styles.css"/>d-Xylose
Template:Chembox image sbs cell
Template:Longitem Template:Unbulleted list
ChEBI Template:Unbulleted list
ChemSpider Template:Unbulleted list
DrugBank Template:Unbulleted list
EC Number Template:Unbulleted list
KEGG Template:Unbulleted list
Template:Longitem Template:Unbulleted list
RTECS number Template:Unbulleted list
Script error: No such module "collapsible list".
Script error: No such module "collapsible list".
Template:Longitem Template:Chem/link
Molar mass 150.13 g/mol
Appearance monoclinic needles or prisms, colourless
Density 1.525 g/cm3 (20 °C)
Melting point Template:Chembox CalcTemperatures
Template:Longitem +22.5° (Template:Chem/link)
Template:Longitem −84.80·10−6 cm3/mol
Template:Longitem Arabinose
Ribose
Lyxose
Template:Longitem Xylulose

Template:Chembox Footer/tracking container onlyScript error: No such module "TemplatePar".Template:Short description

Xylose (cf. Template:Langx, Script error: No such module "lang"., "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.[2] It is a white, water-soluble solid.

Structure

The acyclic form of xylose has chemical formula Template:Chem/link. Cyclic hemiacetal isomers are more prevalent in solution. These cyclic isomers include the pyranoses feature six-membered Template:Chem2 rings, and the furanoses, which feature five-membered Template:Chem/link rings (with a pendant Template:Chem/link group). Each of these rings is subject to further isomerism, depending on the relative orientation of the anomeric hydroxy group.

The dextrorotary form, <templatestyles src="smallcaps/styles.css"/>d-xylose, is the one that usually occurs endogenously in living things. A levorotary form, <templatestyles src="smallcaps/styles.css"/>l-xylose, can be 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 embryos of most edible plants. It was first isolated from wood by Finnish scientist, Koch, in 1881,[3] but first became commercially viable, with a price close to sucrose, in 1930.[4]

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.[5]

Xylose is also found in some species of Chrysolinina beetles, including Chrysolina coerulans. They have cardiac glycosides (including xylose) in their defensive glands.[6]

Applications

Chemicals

The acid-catalysed degradation of hemicellulose gives furfural,[7][8] a precursor to synthetic polymers and to tetrahydrofuran.[9]

Human consumption

Xylose is not a major human nutrient and is largely excreted by the kidneys.[10] An oxidoreductase pathway is present in eukaryotic microorganisms. Humans have enzymes called protein xylosyltransferases (XYLT1, XYLT2) which transfer xylose from UDP to a serine in the core protein of proteoglycans.

Xylose contains 2.4 calories per gram[11] (lower than glucose or sucrose, approx. 4 calories per gram).

Animal medicine

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.[12]

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.[13]

Derivatives

Reduction of xylose by catalytic hydrogenation produces the sugar substitute xylitol.

See also

References

<templatestyles src="Reflist/styles.css" />

  1. ↑ Script error: No such module "citation/CS1".
  2. ↑ Script error: No such module "Citation/CS1".
  3. ↑ Script error: No such module "citation/CS1".
  4. ↑ Script error: No such module "Citation/CS1".
  5. ↑ Script error: No such module "citation/CS1".
  6. ↑ Script error: No such module "citation/CS1".
  7. ↑ Script error: No such module "Citation/CS1".; Script error: No such module "citation/CS1"..
  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Template:Ullmann
  10. ↑ Template:Cite thesis
  11. ↑ <templatestyles src="Citation/styles.css"/>Template:Citation/make link, "Method of producing xylose", issued Script error: No such module "auto date formatter". Script error: No such module "Check for unknown parameters".
  12. ↑ Script error: No such module "citation/CS1".
  13. ↑ Script error: No such module "Citation/CS1".

Script error: No such module "Check for unknown parameters".

Script error: No such module "Navbox".

Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Xylose&oldid=5276132"