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Galactose metabolism

D-Galactose
Galactose-3D-balls.png
Beta-D-Galactopyranose.svg
DGalactose Fischer.svg
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
KEGG
MeSH Galactose
PubChem CID
UNII
Properties
C6H12O6
Molar mass 180.156 g mol−1
Density 1.723 g/cm3
Melting point 167 °C (333 °F; 440 K)
683.0 g/L
-103.00·10−6 cm3/mol
Pharmacology
V04CE01 (WHO) V08DA02 (WHO) (microparticles)
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 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform 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
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YesYN ?)
Infobox references

Galactose ( + , "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is less sweet than glucose and fructose. It is a C-4 epimer of glucose.

Galactan is a polymeric form of galactose found in hemicellulose. Galactan can be converted to galactose by hydrolysis.

Galactose exists in both open-chain and cyclic form. The open-chain form has a carbonyl at the end of the chain.

Four isomers are cyclic, two of them with a pyranose (six-membered) ring, two with a furanose (five-membered) ring. Galactofuranose occurs in bacteria, fungi and protozoa , and is recognized by a putative chordate immune lectin intelectin through its exocyclic 1,2-diol. In the cyclic form there are two anomers, named alpha and beta, since the transition from the open-chain form to the cyclic form involves the creation of a new stereocenter at the site of the open-chain carbonyl. In the beta form, the alcohol group is in the equatorial position, whereas in the alpha form, the alcohol group is in the axial position.

Galactose is a monosaccharide. When combined with glucose (monosaccharide), through a condensation reaction, the result is the disaccharide lactose. The hydrolysis of lactose to glucose and galactose is catalyzed by the enzymes lactase and β-galactosidase. The latter is produced by the lac operon in Escherichia coli.


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Wikipedia

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