EC - Lactose synthase

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IntEnz Enzyme Nomenclature


Accepted name:
lactose synthase
Other names:
N-acetyllactosamine synthase
UDP-galactose—glucose galactosyltransferase
lactose synthetase
uridine diphosphogalactose-glucose galactosyltransferase
UDP-galactose:D-glucose 4-β-D-galactotransferase
UDP-galactose:D-glucose 4-β-D-galactosyltransferase
Systematic name:
UDP-α-D-galactose:D-glucose 4-β-D-galactosyltransferase



The enzyme is a complex of two proteins, A and B. In the absence of the B protein (α-lactalbumin), the enzyme catalyses the transfer of galactose from UDP-galactose to N-acetylglucosamine (EC N-acetyllactosamine synthase).

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB
Gene Ontology: GO:0004461
CAS Registry Number: 9030-11-9


  1. Fitzgerald, D.K., Brodbeck, U., Kiyosawa, I., Mawal, R., Colvin, B. and Ebner, K.E.
    α-Lactalbumin and the lactose synthetase reaction.
    J. Biol. Chem. 245: 2103-2108 (1970). [PMID: 5440844]
  2. Hill, R.L. and Brew, K.
    Lactose synthetase.
    Adv. Enzymol. Relat. Areas Mol. Biol. 43: 411-490 (1975). [PMID: 812340]
  3. Watkins, W.M. and Hassid, W.Z.
    The synthesis of lactose by particulate enzyme preparations from guinea pig and bovine mammary glands.
    J. Biol. Chem. 237: 1432-1440 (1962). [PMID: 14005251]

[EC created 1965]