β1,4-galactosyltransferase 1 was the first mammalian glycosyltransferase to be isolated and cloned. β4GalT1 is a member of a homologous family of seven β1,4-galactosyltransferases, β4Gal-T1 - T7, that catalyze the transfer of galactose from UDP-Gal to acceptor sugars including GlcNAc (the acceptor substrate for β4GalT1), Glc and Xyl. β4GalT1 exists as a membrane bound form and as a shed/secreted form deriving from proteolytic cleavage in the stalk region. β4GalT1 may form a heterodimer with α-Lactalbumin, and the complex catalyzes the reaction of UDP-Gal + glucose -> lactose + UDP. MW: 35 kDa. Purity > 90%