label: galactosylxylosylprotein 3-beta-galactosyltransferase activity
label_lc: galactosylxylosylprotein 3-beta-galactosyltransferase activity
description: "Catalysis of the reaction: 4-beta-D-galactosyl-O-beta-D-xylosylprotein + UDP-galactose = 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosylprotein + UDP."