GO:0047220

galactosylxylosylprotein 3-beta-galactosyltransferase activity

Details: 
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. [EC:2.4.1.134, MetaCyc:2.4.1.134-RXN]
Evidence Code: