2.02012-05-31 10:23:10 -06002015-09-13 12:56:06 -0600ECMDB00186M2MDB000076alpha-LactoseAlpha-Lactose is the alpha anomoer of lactose. It is a disaccharide that consists of galactose and glucose joined by an acetal oxygen bridge in the beta orientation Lactose is a sugar substrate that can be readily used by E. coli. The consumption of lactose by E. coli is controlled by the lac operon. The operon includes beta-galactosidase, lactose permease, and thiogalactoside transacetylase. The lactose permease, which sits in the cytoplasmic membrane, transports lactose into the cell. Beta-galactosidase, a cytoplasmic enzyme, subsequently cleaves lactose into glucose and galactose.α-D-lactoseα-lactose(+)-lactose1-b-D-Galactopyranosyl-4-a-D-glucopyranose1-b-delta-Galactopyranosyl-4-a-delta-glucopyranose1-b-δ-Galactopyranosyl-4-a-δ-glucopyranose1-beta-D-Galactopyranosyl-4-alpha-D-glucopyranose1-beta-delta-Galactopyranosyl-4-alpha-delta-glucopyranose1-β-D-Galactopyranosyl-4-α-D-glucopyranose1-β-δ-Galactopyranosyl-4-α-δ-glucopyranose4-O-HexopyranosylhexoseA-D-LactoseA-LactoseAletobioseAlpha-D-LactoseAlpha-LactoseAnhydrous lactoseDilactoseFast-Flo LactoseFlowlac 100GalactinumGlc-(4-1)GalGranulac 140MLactinLactin (carbohydrate)Lactin (carbohydric acid)LactobioseLactohale 300LactoseLactose anhydrideLactose Fast-floMilk sugarOsmolactanPharmatosa DCL 21Pharmatose 21Pharmatose 325MPharmatose DCL 15PrismalacRespitose ML 003Respitose SV 003Saccharum lactinSachelacSorbalac 400Sorbolac 400SpherolacSuper-TabTablettoseTablettose 70Tablettose 80Zeparox EPα-D-Lactoseα-LactoseC12H22O11342.2965342.116211546(2R,3R,4S,5R,6S)-2-(hydroxymethyl)-6-{[(2R,3S,4R,5R,6S)-4,5,6-trihydroxy-2-(hydroxymethyl)oxan-3-yl]oxy}oxane-3,4,5-triolα-lactose63-42-3OC[C@H]1O[C@@H](O[C@H]2[C@H](O)[C@@H](O)[C@@H](O)O[C@@H]2CO)[C@H](O)[C@@H](O)[C@H]1OInChI=1S/C12H22O11/c13-1-3-5(15)6(16)9(19)12(22-3)23-10-4(2-14)21-11(20)8(18)7(10)17/h3-20H,1-2H2/t3-,4-,5+,6+,7-,8-,9-,10-,11+,12+/m1/s1GUBGYTABKSRVRQ-XLOQQCSPSA-NSolidCytosolExtra-organismPeriplasmlogp-3.01logs0.23solubility5.86e+02 g/lmelting_point201-202 oClogp-4.7pka_strongest_acidic11.25pka_strongest_basic-3iupac(2R,3R,4S,5R,6S)-2-(hydroxymethyl)-6-{[(2R,3S,4R,5R,6S)-4,5,6-trihydroxy-2-(hydroxymethyl)oxan-3-yl]oxy}oxane-3,4,5-triolaverage_mass342.2965mono_mass342.116211546smilesOC[C@H]1O[C@@H](O[C@H]2[C@H](O)[C@@H](O)[C@@H](O)O[C@@H]2CO)[C@H](O)[C@@H](O)[C@H]1OformulaC12H22O11inchiInChI=1S/C12H22O11/c13-1-3-5(15)6(16)9(19)12(22-3)23-10-4(2-14)21-11(20)8(18)7(10)17/h3-20H,1-2H2/t3-,4-,5+,6+,7-,8-,9-,10-,11+,12+/m1/s1inchikeyGUBGYTABKSRVRQ-XLOQQCSPSA-Npolar_surface_area189.53refractivity68.34polarizability30.92rotatable_bond_count4acceptor_count11donor_count8physiological_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
PW000821ec00052MetabolicPhosphotransferase system (PTS)ec02060ABC transportersec02010Lac OperonWhen glucose is absent and lactose is present in the environment, cyclic AMP is present and binds to the catabolite activator protein (CAP) which in turn binds to the activator binding site and facilitates transcription.
Lactose binds to the repressor and prevents it from binding to the operator site.
RNA polymerase can now bind to the promoter and carry out transcription of the lac operon.
PW000955SignalingLac Operon Inactivation 1When glucose is present, the concentration of cyclic AMP in the cell is low, hence cyclic AMP does not bind to the catabolite activator protein. This leads to the CAP-CAMP complex does not bind to the activator binding site. Therefore RNA polymerase can't bind efficiently to the promoter and transcription does not occur.PW000957SignalingLac Operon Inactivation 2When neither glucose nor lactose is present in the media cell, the concentration of cyclic AMP is high and the catabolite activator protein is bound to the activator binding site, But even though RNA polymerase can bind to the promoter, it is blocked by the repressor on the operator site. Hence there is no transcription of the lac operonPW000956Signalinggalactose 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 addedPW000786Metaboliclactose degradation IIIBGALACT-PWYSpecdb::CMs426Specdb::CMs427Specdb::CMs428Specdb::CMs23173Specdb::CMs37343Specdb::CMs148314Specdb::CMs148316Specdb::CMs148318Specdb::CMs148320Specdb::CMs148322Specdb::CMs148324Specdb::CMs148327Specdb::CMs148328Specdb::CMs148331Specdb::CMs164052Specdb::CMs279669Specdb::CMs1052873Specdb::CMs1052875Specdb::CMs1052877Specdb::CMs1052878Specdb::CMs1052881Specdb::CMs1052883Specdb::CMs1052884Specdb::CMs1052886Specdb::CMs1052888Specdb::NmrOneD1154Specdb::NmrOneD1196Specdb::NmrOneD6052Specdb::NmrOneD6053Specdb::NmrOneD6054Specdb::NmrOneD6055Specdb::NmrOneD6056Specdb::NmrOneD6057Specdb::NmrOneD6058Specdb::NmrOneD6059Specdb::NmrOneD6060Specdb::NmrOneD6061Specdb::NmrOneD6062Specdb::NmrOneD6063Specdb::NmrOneD6064Specdb::NmrOneD6065Specdb::NmrOneD6066Specdb::NmrOneD6067Specdb::NmrOneD6068Specdb::NmrOneD6069Specdb::NmrOneD6070Specdb::NmrOneD6071Specdb::NmrOneD166517Specdb::MsMs292Specdb::MsMs293Specdb::MsMs294Specdb::MsMs317407Specdb::MsMs317408Specdb::MsMs317409Specdb::MsMs363868Specdb::MsMs363869Specdb::MsMs363870Specdb::MsMs2729182Specdb::MsMs2729183Specdb::MsMs2729184Specdb::MsMs2980160Specdb::MsMs2980161Specdb::MsMs2980162Specdb::NmrTwoD986Specdb::NmrTwoD1192HMDB001868457176293C0024336219LACTOSELBTLactoseKeseler, I. M., Collado-Vides, J., Santos-Zavaleta, A., Peralta-Gil, M., Gama-Castro, S., Muniz-Rascado, L., Bonavides-Martinez, C., Paley, S., Krummenacker, M., Altman, T., Kaipa, P., Spaulding, A., Pacheco, J., Latendresse, M., Fulcher, C., Sarker, M., Shearer, A. G., Mackie, A., Paulsen, I., Gunsalus, R. P., Karp, P. D. (2011). "EcoCyc: a comprehensive database of Escherichia coli biology." Nucleic Acids Res 39:D583-D590.21097882Kanehisa, M., Goto, S., Sato, Y., Furumichi, M., Tanabe, M. (2012). "KEGG for integration and interpretation of large-scale molecular data sets." Nucleic Acids Res 40:D109-D114.22080510van der Werf, M. J., Overkamp, K. M., Muilwijk, B., Coulier, L., Hankemeier, T. (2007). "Microbial metabolomics: toward a platform with full metabolome coverage." Anal Biochem 370:17-25.17765195Winder, C. L., Dunn, W. B., Schuler, S., Broadhurst, D., Jarvis, R., Stephens, G. M., Goodacre, R. (2008). 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Metabolic Engineering (2006), 8(5), 465-473.http://hmdb.ca/system/metabolites/msds/000/000/130/original/HMDB00186.pdf?1358463298Beta-galactosidaseP00722BGAL_ECOLIlacZhttp://ecmdb.ca/proteins/P00722.xmlEvolved beta-galactosidase subunit alphaP06864BGA2_ECOLIebgAhttp://ecmdb.ca/proteins/P06864.xmlPeriplasmic beta-glucosidaseP33363BGLX_ECOLIbglXhttp://ecmdb.ca/proteins/P33363.xmlcryptic beta-D-galactosidase, beta subunitP0AC73ebgChttp://ecmdb.ca/proteins/P0AC73.xmlBeta-galactosidaseG0ZKW2G0ZKW2_ECOLIlacZhttp://ecmdb.ca/proteins/G0ZKW2.xmlSugar efflux transporter AP31675SETA_ECOLIsetAhttp://ecmdb.ca/proteins/P31675.xmlSugar efflux transporter BP33026SETB_ECOLIsetBhttp://ecmdb.ca/proteins/P33026.xmlSugar efflux transporter CP31436SETC_ECOLIsetChttp://ecmdb.ca/proteins/P31436.xmlLactose permeaseP02920LACY_ECOLIlacYhttp://ecmdb.ca/proteins/P02920.xmlSugar efflux transporterP31122SOTB_ECOLIsotBhttp://ecmdb.ca/proteins/P31122.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.xmlWater + alpha-Lactose > D-Galactose + D-Glucosealpha-Lactose + Water <> alpha-D-Glucose + D-GalactoseR01678Water + alpha-Lactose > D-Galactose + b-D-GlucoseBETAGALACTOSID-RXNalpha-Lactose AllolactoseRXN0-5363alpha-Lactose + Water > beta-D-Galactose + Beta-D-Glucose + b-D-GlucosePW_R002956