Reaction: UDP-α-D-galactose + D-glucose = UDP + lactose
Other name(s): UDP-α-D-galactose—glucose galactosyltransferase; N-acetyllactosamine synthase; uridine diphosphogalactose-glucose galactosyltransferase; lactose synthetase; 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
Comments: 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 2.4.1.90 N-acetyllactosamine synthase).
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9030-11-9
References:
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 (1970) 2103-2108. [PMID: 5440844]
2. Hill, R.L. and Brew, K. Lactose synthetase. Adv. Enzymol. Relat. Areas Mol. Biol. 43 (1975) 411-490. [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 (1962) 1432-1440.