2.02012-05-31 14:02:34 -06002015-09-13 12:56:13 -0600ECMDB04025M2MDB000565beta-D-GalactoseGalactose is an optical isomer of glucose. An aldohexose that occurs naturally in the D-form in lactose, cerebrosides, gangliosides, and mucoproteins. Galactose is less sweet than glucose and not very water-soluble. Galactose is a monosaccharide constituent, together with glucose, of the disaccharide lactose. Galactose is produced by hydrolysis of lactose by galactosidase. This enzyme is produced by the lac operon in Escherichia coli (E. coli). Galactan is a polymer of the sugar galactose. It is found in hemicellulose and can be converted to galactose by hydrolysis.6-(Hydroxymethyl)tetrahydropyran-2,3,4,5-tetraolb D-Galactoseb-D-GalactopyranoseB-D-GalactoseB-D-Galactosideb-D-Galactosidesb-delta-Galactosideb-delta-GalactosidesB-Galactoseb-δ-Galactosideb-δ-GalactosidesBeta D-GalactoseBeta-D-GalactopyranoseBeta-D-GalactoseBeta-D-GalactosideBeta-D-GalactosidesBeta-delta-GalactosideBeta-delta-galactosidesBeta-GalactoseCerebroseD-galactoseDelta-GalactoseGalactopyranoseGalactopyranosideGalactoseβ D-Galactoseβ-D-Galactopyranoseβ-D-Galactoseβ-D-Galactosideβ-D-Galactosidesβ-Galactoseβ-δ-Galactosideβ-δ-Galactosidesδ-GalactoseC6H12O6180.1559180.063388116(2R,3R,4S,5R,6R)-6-(hydroxymethyl)oxane-2,3,4,5-tetrolβ D-galactose7296-64-2OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@H]1OInChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3+,4+,5-,6-/m1/s1WQZGKKKJIJFFOK-FPRJBGLDSA-NSolidExtra-organismPeriplasmlogp-2.57logs0.64solubility7.82e+02 g/llogp-2.9pka_strongest_acidic11.3pka_strongest_basic-3iupac(2R,3R,4S,5R,6R)-6-(hydroxymethyl)oxane-2,3,4,5-tetrolaverage_mass180.1559mono_mass180.063388116smilesOC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@H]1OformulaC6H12O6inchiInChI=1S/C6H12O6/c7-1-2-3(8)4(9)5(10)6(11)12-2/h2-11H,1H2/t2-,3+,4+,5-,6-/m1/s1inchikeyWQZGKKKJIJFFOK-FPRJBGLDSA-Npolar_surface_area110.38refractivity35.92polarizability16.33rotatable_bond_count1acceptor_count6donor_count5physiological_charge0formal_charge0Galactose metabolismGalactose can be synthesized through two pathways: melibiose degradation involving an alpha galactosidase and lactose degradation involving a beta galactosidase. Melibiose is first transported inside the cell through the melibiose:Li+/Na+/H+ symporter. Once inside the cell, melibiose is degraded through alpha galactosidase into an alpha-D-galactose and a beta-D-glucose. The beta-D-glucose is phosphorylated by a glucokinase to produce a beta-D-glucose-6-phosphate which can spontaneously be turned into a alpha D glucose 6 phosphate. This alpha D-glucose-6-phosphate is metabolized into a glucose -1-phosphate through a phosphoglucomutase-1. The glucose -1-phosphate is transformed into a uridine diphosphate glucose through UTP--glucose-1-phosphate uridylyltransferase. The product, uridine diphosphate glucose, can undergo a reversible reaction in which it can be turned into uridine diphosphategalactose through an UDP-glucose 4-epimerase.
Galactose can also be produced by lactose degradation involving a lactose permease to uptake lactose from the environment and a beta-galactosidase to turn lactose into Beta-D-galactose.
Beta-D-galactose can also be uptaken from the environment through a galactose proton symporter.
Galactose is degraded through the following process:
Beta-D-galactose is introduced into the cytoplasm through a galactose proton symporter, or it can be synthesized from an alpha lactose that is introduced into the cytoplasm through a lactose permease. Alpha lactose interacts with water through a beta-galactosidase resulting in a beta-D-glucose and beta-D-galactose. Beta-D-galactose is isomerized into D-galactose. D-Galactose undergoes phosphorylation through a galactokinase, hence producing galactose 1 phosphate. On the other side of the pathway, a gluose-1-phosphate (product of the interaction of alpha-D-glucose 6-phosphate with a phosphoglucomutase resulting in a alpha-D-glucose-1-phosphate, an isomer of Glucose 1-phosphate, or an isomer of Beta-D-glucose 1-phosphate) interacts with UTP and a hydrogen ion in order to produce a uridine diphosphate glucose. This is followed by the interaction of galactose-1-phosphate with an established amount of uridine diphosphate glucose through a galactose-1-phosphate uridylyltransferase, which in turn output a glucose-1-phosphate and a uridine diphosphate galactose. The glucose -1-phosphate is transformed into a uridine diphosphate glucose through UTP--glucose-1-phosphate uridylyltransferase. The product, uridine diphosphate glucose, can undergo a reversible reaction in which it can be turned into uridine diphosphategalactose through an UDP-glucose 4-epimerase, and so the cycle can keep going as long as more lactose or galactose is imported into the cell
PW000821ec00052Metabolicgalactose degradation/Leloir PathwayThe degradation of galactose, also known as Leloir pathway, requires 3 main enzymes once Beta-D-galactose has been converted to galactose through an Aldose-1-epimerase. These are: galactokinase , galactose-1-phosphate uridylyltransferase and UDP-glucose 4-epimerase. Beta-D-galactose can be uptaken from the environment through a galactose proton symporter. It can also be produced by lactose degradation involving a lactose permease to uptake lactose from the environment and a beta-galactosidase to turn lactose into Beta-D-galactose.
Galactose is degraded through the following process:
Beta-D-galactose is introduced into the cytoplasm through a galactose proton symporter, or it can be synthesized from an alpha lactose that is introduced into the cytoplasm through a lactose permease. Alpha lactose interacts with water through a beta-galactosidase resulting in a beta-D-glucose and beta-D-galactose. Beta-D-galactose is isomerized into D-galactose. D-Galactose undergoes phosphorylation through a galactokinase, hence producing galactose 1 phosphate. On the other side of the pathway, a gluose-1-phosphate (product of the interaction of alpha-D-glucose 6-phosphate with a phosphoglucomutase resulting in a alpha-D-glucose-1-phosphate, an isomer of Glucose 1-phosphate, or an isomer of Beta-D-glucose 1-phosphate) interacts with UTP and a hydrogen ion in order to produce a uridine diphosphate glucose. This is followed by the interaction of galactose-1-phosphate with an established amount of uridine diphosphate glucose through a galactose-1-phosphate uridylyltransferase, which in turn output a glucose-1-phosphate and a uridine diphosphate galactose. The glucose -1-phosphate is transformed into a uridine diphosphate glucose through UTP--glucose-1-phosphate uridylyltransferase. The product, uridine diphosphate glucose, can undergo a reversible reaction in which it can be turned into uridine diphosphategalactose through an UDP-glucose 4-epimerase, and so the cycle can keep going as long as more lactose or galactose is imported into the cell.
PW000884Metabolicinner membrane transportlist of inner membrane transport complexes, transporting compounds from the periplasmic space to the cytosol
This pathway should be updated regularly with the new inner membrae transports addedPW000786Metabolicgalactose degradation I (Leloir pathway)GALACTMETAB-PWYlactose degradation IIIBGALACT-PWYSpecdb::CMs2500Specdb::CMs38603Specdb::CMs160259Specdb::NmrOneD21902Specdb::NmrOneD21903Specdb::NmrOneD21904Specdb::NmrOneD21905Specdb::NmrOneD21906Specdb::NmrOneD21907Specdb::NmrOneD21908Specdb::NmrOneD21909Specdb::NmrOneD21910Specdb::NmrOneD21911Specdb::NmrOneD21912Specdb::NmrOneD21913Specdb::NmrOneD21914Specdb::NmrOneD21915Specdb::NmrOneD21916Specdb::NmrOneD21917Specdb::NmrOneD21918Specdb::NmrOneD21919Specdb::NmrOneD21920Specdb::NmrOneD21921Specdb::MsMs2316Specdb::MsMs2317Specdb::MsMs2318Specdb::MsMs182655Specdb::MsMs182656Specdb::MsMs182657Specdb::MsMs183003Specdb::MsMs183004Specdb::MsMs183005Specdb::MsMs1471166Specdb::MsMs2423147Specdb::MsMs2423148Specdb::MsMs2423149Specdb::MsMs2513234Specdb::MsMs2513235Specdb::MsMs2513236HMDB03449439353388476C00962GALACTOSEGLBGALKeseler, I. 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Journal of the American Chemical Society (1957), 79 3868-71. http://hmdb.ca/system/metabolites/msds/000/003/030/original/HMDB03449.pdf?1358461766Beta-galactosidaseP00722BGAL_ECOLIlacZhttp://ecmdb.ca/proteins/P00722.xmlAldose 1-epimeraseP0A9C3GALM_ECOLIgalMhttp://ecmdb.ca/proteins/P0A9C3.xmlABC transporter periplasmic-binding protein ytfQP39325YTFQ_ECOLIytfQhttp://ecmdb.ca/proteins/P39325.xmlGalactoside transport system permease protein mglCP23200MGLC_ECOLImglChttp://ecmdb.ca/proteins/P23200.xmlMelibiose carrier proteinP02921MELB_ECOLImelBhttp://ecmdb.ca/proteins/P02921.xmlSugar efflux transporter AP31675SETA_ECOLIsetAhttp://ecmdb.ca/proteins/P31675.xmlSugar efflux transporter CP31436SETC_ECOLIsetChttp://ecmdb.ca/proteins/P31436.xmlABC transporter periplasmic-binding protein ytfQP39325YTFQ_ECOLIytfQhttp://ecmdb.ca/proteins/P39325.xmlGalactoside transport system permease protein mglCP23200MGLC_ECOLImglChttp://ecmdb.ca/proteins/P23200.xmlOuter membrane protein NP77747OMPN_ECOLIompNhttp://ecmdb.ca/proteins/P77747.xmlOuter membrane pore protein EP02932PHOE_ECOLIphoEhttp://ecmdb.ca/proteins/P02932.xmlOuter membrane protein FP02931OMPF_ECOLIompFhttp://ecmdb.ca/proteins/P02931.xmlOuter membrane protein CP06996OMPC_ECOLIompChttp://ecmdb.ca/proteins/P06996.xmlbeta-D-Galactose > D-GalactoseAlpha-D-Galactose > beta-D-GalactosePW_R002953beta-D-Galactose > Alpha-D-GalactosePW_R002954alpha-Lactose + Water > beta-D-Galactose + Beta-D-Glucose + b-D-GlucosePW_R002956