Galactose

D-Galactose

Identifiers
CAS Number	59-23-4 N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:28061 Y
ChEMBL	ChEMBL300520 N
ChemSpider	388480 Y
IUPHAR/BPS	4646
KEGG	D04291 N
MeSH	Galactose
PubChem	439357
UNII	X2RN3Q8DNE Y
InChI InChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2−,3+,4+,5−,6+/m1/s1 Y Key: WQZGKKKJIJFFOK-PHYPRBDBSA-N Y InChI=1/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2−,3+,4+,5−,6+/m1/s1 Key: WQZGKKKJIJFFOK-PHYPRBDBBU
SMILES O[C@H]1[C@@H](O)[C@H](O[C@H](O)[C@@H]1O)CO
Properties
Chemical formula	C6H12O6
Molar mass	180.156 g mol−1
Density	1.723 g/cm3
Melting point	167 °C (333 °F; 440 K)
Solubility in water	683.0 g/L
Magnetic susceptibility (χ)	-103.00·10−6 cm3/mol
Pharmacology
ATC code	V04CE01 (WHO) V08DA02 (WHO) (microparticles)
Hazards
NFPA 704	1 2 0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
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.