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Record Information
Creation Date2005-11-16 15:48:42 UTC
Update Date2016-02-11 01:02:11 UTC
Secondary Accession Numbers
  • HMDB05761
Metabolite Identification
Common NameAlpha-Lactose
Descriptionalpha-Lactose is the major sugar present in milk and the main source of energy supplied to the newborn mammalian in its mother's milk. Lactose is also an important osmotic regulator of lactation. It is digested by the intestinal lactase (EC, an enzyme expressed in newborns. Its activity declines following weaning. As a result, adult mammals are normally lactose-intolerant and more than 75% of the human adult population suffers from lactase deficiency. Lactase deficiency is present in up to 80 percent of blacks and Latinos, and up to 100 percent of American Indians and Asians. Persons with lactose intolerance are unable to digest significant amounts of lactose. Common symptoms include abdominal pain and bloating, excessive flatus, and watery stool following the ingestion of foods containing lactose. A sizable number of adults believe they are lactose intolerant but do not actually have impaired lactose digestion, and some persons with lactase deficiency can tolerate moderate amounts of ingested lactose. A diagnosis of lactose intolerance can usually be made with a careful history supported by dietary manipulation. If necessary, diagnosis can be confirmed by using a breath hydrogen or lactose tolerance test. These mostly uncomfortable symptoms of lactose maldigestion are blamed for a variably dairy consumption. There is, however, emerging evidence that certain lactic acid-producing bacteria, which selectively consume prebiotics, may be beneficial against some lower intestinal diseases. Lactose maldigestion and lactose should perhaps be re-evaluated as a potential provider of such a prebiotic. Treatment consists primarily of avoiding lactose-containing foods. Lactase enzyme supplements may be helpful. The degree of lactose malabsorption varies greatly among patients with lactose intolerance, but most of them can ingest up to 350 mL of milk daily without symptoms. Lactose-intolerant patients must ensure adequate calcium intake. (PMID: 13130292 , 12216958 , 12197838 , 12018807 ).
  1. (+)-lactose
  2. 1-beta-D-Galactopyranosyl-4-alpha-D-glucopyranose
  3. 1-beta-delta-Galactopyranosyl-4-alpha-delta-glucopyranose
  4. 4-O-Hexopyranosylhexose
  5. a-Lactose
  6. Aletobiose
  7. alpha-Lactose
  8. Anhydrous lactose
  9. Dilactose
  10. Fast-Flo Lactose
  11. Flowlac 100
  12. Galactinum
  13. Glc-(4-1)Gal
  14. Granulac 140M
  15. Lactin
  16. Lactin (carbohydrate)
  17. Lactobiose
  18. Lactohale 300
  19. Lactose
  20. Lactose anhydride
  21. Lactose Fast-flo
  22. Milk sugar
  23. Osmolactan
  24. Pharmatosa DCL 21
  25. Pharmatose 21
  26. Pharmatose 325M
  27. Pharmatose DCL 15
  28. Prismalac
  29. Respitose ML 003
  30. Respitose SV 003
  31. Saccharum lactin
  32. Sachelac
  33. Sorbalac 400
  34. Sorbolac 400
  35. Spherolac
  36. Super-Tab
  37. Tablettose
  38. Tablettose 70
  39. Tablettose 80
  40. Zeparox EP
Chemical FormulaC12H22O11
Average Molecular Weight342.2965
Monoisotopic Molecular Weight342.116211546
IUPAC Name(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-triol
Traditional Nameα-lactose
CAS Registry Number63-42-3
InChI Identifier
Chemical Taxonomy
DescriptionThis compound belongs to the class of organic compounds known as o-glycosyl compounds. These are glycoside in which a sugar group is bonded through one carbon to another group via a O-glycosidic bond.
KingdomOrganic compounds
Super ClassOrganooxygen compounds
ClassCarbohydrates and carbohydrate conjugates
Sub ClassGlycosyl compounds
Direct ParentO-glycosyl compounds
Alternative Parents
  • O-glycosyl compound
  • Disaccharide
  • Oxane
  • Secondary alcohol
  • Polyol
  • Hemiacetal
  • 1,2-diol
  • Oxacycle
  • Organoheterocyclic compound
  • Acetal
  • Hydrocarbon derivative
  • Primary alcohol
  • Alcohol
  • Aliphatic heteromonocyclic compound
Molecular FrameworkAliphatic heteromonocyclic compounds
External Descriptors
StatusDetected and Quantified
  • Endogenous
  • Component of Galactose metabolism
  • Component of Glycerolipid metabolism
  • Component of Glycosphingolipid metabolism
  • Component of Keratan sulfate biosynthesis
  • Component of N-Glycan biosynthesis
ApplicationNot Available
Cellular locations
  • Cytoplasm
  • Extracellular
  • Lysosome
  • Golgi apparatus
Physical Properties
Experimental Properties
Melting Point201 - 202 °CNot Available
Boiling PointNot AvailableNot Available
Water Solubility195 mg/mL at 20 °CNot Available
LogPNot AvailableNot Available
Predicted Properties
Water Solubility586.0 mg/mLALOGPS
pKa (Strongest Acidic)11.25ChemAxon
pKa (Strongest Basic)-3ChemAxon
Physiological Charge0ChemAxon
Hydrogen Acceptor Count11ChemAxon
Hydrogen Donor Count8ChemAxon
Polar Surface Area189.53 Å2ChemAxon
Rotatable Bond Count4ChemAxon
Refractivity68.34 m3·mol-1ChemAxon
Polarizability30.96 Å3ChemAxon
Number of Rings2ChemAxon
Rule of FiveYesChemAxon
Ghose FilterYesChemAxon
Veber's RuleYesChemAxon
MDDR-like RuleYesChemAxon
Spectrum TypeDescriptionSplash Key
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (8 TMS)splash10-3zta000000-af8ca1bf1faa3d01a08dView in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (8 TMS; 1 MEOX)splash10-zth5000000-a61bf0223a1683f0402eView in MoNA
GC-MSGC-MS Spectrum - GC-EI-TOF (Pegasus III TOF-MS system, Leco; GC 6890, Agilent Technologies) (8 TMS; 1 MEOX)splash10-zqg4000000-12611bfab50cb066e8afView in MoNA
LC-MS/MSLC-MS/MS Spectrum - Quattro_QQQ 10V, Positive (Annotated)splash10-1z05000000-bcb7aaa42261d980d488View in MoNA
LC-MS/MSLC-MS/MS Spectrum - Quattro_QQQ 25V, Positive (Annotated)splash10-ze00000000-1bc18b05388cd2213573View in MoNA
LC-MS/MSLC-MS/MS Spectrum - Quattro_QQQ 40V, Positive (Annotated)splash10-z300000000-4483af567feecb34a651View in MoNA
1D NMR1H NMR SpectrumNot Available
1D NMR13C NMR SpectrumNot Available
2D NMR[1H,1H] 2D NMR SpectrumNot Available
2D NMR[1H,13C] 2D NMR SpectrumNot Available
Biological Properties
Cellular Locations
  • Cytoplasm
  • Extracellular
  • Lysosome
  • Golgi apparatus
Biofluid Locations
  • Blood
  • Breast Milk
  • Feces
  • Urine
Tissue Location
  • Bladder
  • Gut
  • Intestine
  • Muscle
  • Platelet
  • Skin
  • Spleen
Congenital disorder of glycosylation CDG-IIdSMP00579Not Available
Galactose MetabolismSMP00043map00052
GalactosemiaSMP00182Not Available
GLUT-1 deficiency syndromeSMP00580Not Available
Lactose DegradationSMP00457Not Available
Lactose IntoleranceSMP00458Not Available
Lactose SynthesisSMP00444Not Available
Normal Concentrations
BloodExpected but not QuantifiedNot ApplicableNot AvailableNot Available
  • Not Applicable
Breast MilkDetected and Quantified170000 +/- 7300 uMAdult (>18 years old)Female
FecesDetected but not QuantifiedNot ApplicableInfant (0-1 year old)Both
UrineDetected and Quantified19.378 +/- 10.997 umol/mmol creatinineChildren (1 - 13 years old)Not Specified
    • Mordechai, Hien, ...
UrineDetected and Quantified11.8 (1.0-24.2) umol/mmol creatinineAdult (>18 years old)Both
UrineDetected and Quantified30.0 (13.0-49.0) umol/mmol creatinineInfant (0-1 year old)BothNormal
    • Geigy Scientific ...
UrineDetected and Quantified1.45 (0.63-3.45) umol/mmol creatinineAdult (>18 years old)BothNormal
    • Geigy Scientific ...
UrineDetected and Quantified36.31 +/- 6.60 umol/mmol creatinineAdult (>18 years old)Not Specified
UrineDetected and Quantified66.02 +/- 6.60 umol/mmol creatinineAdult (>18 years old)Not Specified
UrineDetected and Quantified676.75 +/- 85.83 umol/mmol creatinineNewborn (0-30 days old)Not Specified
UrineDetected and Quantified6.08 +/- 6.07 umol/mmol creatinineInfant (0-1 year old)BothNormal details
Abnormal Concentrations
UrineDetected and Quantified51.475 +/- 126.985 umol/mmol creatinineChildren (1 - 13 years old)Not Specified
Eosinophilic esophagitis
    • Mordechai, Hien, ...
Associated Disorders and Diseases
Disease ReferencesNone
Associated OMIM IDsNone
DrugBank IDDB04465
DrugBank Metabolite IDNot Available
Phenol Explorer Compound IDNot Available
Phenol Explorer Metabolite IDNot Available
FoodDB IDFDB001145
KNApSAcK IDC00001136
Chemspider ID76293
KEGG Compound IDC00243
BiGG ID34366
Wikipedia LinkLactose
NuGOwiki LinkHMDB00186
Metagene LinkHMDB00186
PubChem Compound84571
ChEBI ID36219
Synthesis ReferenceRuffing, Anne; Mao, Zichao; Ruizhen Chen, Rachel. Metabolic engineering of Agrobacterium sp. for UDP-galactose regeneration and oligosaccharide synthesis. Metabolic Engineering (2006), 8(5), 465-473.
Material Safety Data Sheet (MSDS)Download (PDF)
General References
  1. Jung SK, Fujimoto D: A novel beta-galactoside-binding lectin in adult rat kidney. J Biochem (Tokyo). 1994 Sep;116(3):547-53. [7852273 ]
  2. Oozeer R, Furet JP, Goupil-Feuillerat N, Anba J, Mengaud J, Corthier G: Differential activities of four Lactobacillus casei promoters during bacterial transit through the gastrointestinal tracts of human-microbiota-associated mice. Appl Environ Microbiol. 2005 Mar;71(3):1356-63. [15746338 ]
  3. Dimopoulos MA, Anagnostopoulos A: Thalidomide in relapsed/refractory multiple myeloma: pivotal trials conducted outside the United States. Semin Hematol. 2003 Oct;40(4 Suppl 4):8-16. [15015891 ]
  4. Muthusamy A, Erickson DR, Sheykhnazari M, Bhavanandan VP: Enhanced binding of modified pentosan polysulfate and heparin to bladder--a strategy for improved treatment of interstitial cystitis. Urology. 2006 Jan;67(1):209-13. [16413377 ]
  5. Johnson JD, Simoons FJ, Hurwitz R, Grange A, Mitchell CH, Sinatra FR, Sunshine P, Robertson WV, Bennett PH, Kretchmer N: Lactose malabsorption among the Pima indians of Arizona. Gastroenterology. 1977 Dec;73(6):1299-304. [578795 ]
  6. Lustenberger RW: [A 23-year old patient with chronic diarrhea. Celiac disease and lactose intolerance] Schweiz Rundsch Med Prax. 2005 Feb 2;94(5):163-4. [15745382 ]
  7. Sharma A, DiCioccio RA, Allen HJ: Identification and synthesis of a novel 15 kDa beta-galactoside-binding lectin in human leukocytes. Glycobiology. 1992 Aug;2(4):285-92. [1421750 ]
  8. Rana SV, Bhasin DK, Vinayak VK: Lactose hydrogen breath test in Giardia lamblia-positive patients. Dig Dis Sci. 2005 Feb;50(2):259-61. [15745082 ]
  9. Mitchell JD, Brand J, Halbisch J: Weight-gain inhibition by lactose in Australian Aboriginal children. A controlled trial of normal and lactose hydrolysed milk. Lancet. 1977 Mar 5;1(8010):500-2. [65606 ]
  10. Soupene E, van Heeswijk WC, Plumbridge J, Stewart V, Bertenthal D, Lee H, Prasad G, Paliy O, Charernnoppakul P, Kustu S: Physiological studies of Escherichia coli strain MG1655: growth defects and apparent cross-regulation of gene expression. J Bacteriol. 2003 Sep;185(18):5611-26. [12949114 ]
  11. Yeoh E, Horowitz M, Russo A, Muecke T, Robb T, Chatterton B: The effects of abdominal irradiation for seminoma of the testis on gastrointestinal function. J Gastroenterol Hepatol. 1995 Mar-Apr;10(2):125-30. [7787155 ]
  12. Bondesson E, Bengtsson T, Borgstrom L, Nilsson LE, Norrgren K, Olsson B, Svensson M, Wollmer P: Dose delivery late in the breath can increase dry powder aerosol penetration into the lungs. J Aerosol Med. 2005 Spring;18(1):23-33. [15741771 ]
  13. Roberson CM: Lactose intolerance. Ala Nurse. 2004 Dec-2005 Feb;31(4):23-4; quiz 24. [15662762 ]
  14. Kim KI, Lee WS, Benevenga NJ: Feeding diets containing high levels of milk products or cellulose decrease urease activity and ammonia production in rat intestine. J Nutr. 1998 Jul;128(7):1186-91. [9649604 ]
  15. Gunther S, Patterson RE, Kristal AR, Stratton KL, White E: Demographic and health-related correlates of herbal and specialty supplement use. J Am Diet Assoc. 2004 Jan;104(1):27-34. [14702580 ]
  16. Delaveau P: [Milk lactose. Hypothesis on its biological importance]. Ann Pharm Fr. 2003;61(5):340-2. [13130292 ]
  17. Vilotte JL: Lowering the milk lactose content in vivo: potential interests, strategies and physiological consequences. Reprod Nutr Dev. 2002 Mar-Apr;42(2):127-32. [12216958 ]
  18. Szilagyi A: Review article: lactose--a potential prebiotic. Aliment Pharmacol Ther. 2002 Sep;16(9):1591-602. [12197838 ]
  19. Swagerty DL Jr, Walling AD, Klein RM: Lactose intolerance. Am Fam Physician. 2002 May 1;65(9):1845-50. [12018807 ]


General function:
Involved in hydrolase activity, hydrolyzing O-glycosyl compounds
Specific function:
LPH splits lactose in the small intestine.
Gene Name:
Uniprot ID:
Molecular weight:
General function:
Involved in transferase activity, transferring glycosyl groups
Specific function:
Responsible for the synthesis of complex-type N-linked oligosaccharides in many glycoproteins as well as the carbohydrate moieties of glycolipids. Can produce lactose.
Gene Name:
Uniprot ID:
Molecular weight:
General function:
Involved in lactose synthase activity
Specific function:
Regulatory subunit of lactose synthase, changes the substrate specificity of galactosyltransferase in the mammary gland making glucose a good acceptor substrate for this enzyme. This enables LS to synthesize lactose, the major carbohydrate component of milk. In other tissues, galactosyltransferase transfers galactose onto the N-acetylglucosamine of the oligosaccharide chains in glycoproteins.
Gene Name:
Uniprot ID:
Molecular weight:
Not Available
General function:
Involved in transferase activity, transferring glycosyl groups
Specific function:
The Golgi complex form catalyzes the production of lactose in the lactating mammary gland and could also be responsible for the synthesis of complex-type N-linked oligosaccharides in many glycoproteins as well as the carbohydrate moieties of glycolipids. The cell surface form functions as a recognition molecule during a variety of cell to cell and cell to matrix interactions, as those occurring during development and egg fertilization, by binding to specific oligosaccharide ligands on opposing cells or in the extracellular matrix.
Gene Name:
Uniprot ID:
Molecular weight:
General function:
Involved in hydrolase activity, hydrolyzing O-glycosyl compounds
Specific function:
Cleaves beta-linked terminal galactosyl residues from gangliosides, glycoproteins, and glycosaminoglycans. Isoform 2 has no beta-galactosidase catalytic activity, but plays functional roles in the formation of extracellular elastic fibers (elastogenesis) and in the development of connective tissue. Seems to be identical to the elastin-binding protein (EBP), a major component of the non-integrin cell surface receptor expressed on fibroblasts, smooth muscle cells, chondroblasts, leukocytes, and certain cancer cell types. In elastin producing cells, associates with tropoelastin intracellularly and functions as a recycling molecular chaperone which facilitates the secretions of tropoelastin and its assembly into elastic fibers.
Gene Name:
Uniprot ID:
Molecular weight:
Not Available
General function:
Involved in glycolipid transporter activity
Specific function:
Accelerates the intermembrane transfer of various glycolipids. Catalyzes the transfer of various glycosphingolipids between membranes but does not catalyze the transfer of phospholipids. May be involved in the intracellular translocation of glucosylceramides
Gene Name:
Uniprot ID:
Molecular weight:
  1. Overington JP, Al-Lazikani B, Hopkins AL: How many drug targets are there? Nat Rev Drug Discov. 2006 Dec;5(12):993-6. [17139284 ]
  2. Imming P, Sinning C, Meyer A: Drugs, their targets and the nature and number of drug targets. Nat Rev Drug Discov. 2006 Oct;5(10):821-34. [17016423 ]