The gene B3GALT6 encodes for the UDP-Gal:βGalβ1-4Xyl β1,3-galactosyltransferase (β3Gal-T6) previously designated the Gal-II synthase catalyzing the third step in the biosynthesis of the proteoglycan linker tetrasaccharide (GlcAβ1-3Galβ1-3Galβ1-4Xylβ1-O-Ser). The β1,3-galactosyltransferase family assigned to CAZy family GT31 contains 6 members, β3Gal-T1, T2, T4, T5, T6, and C1Gal-T1 with different functions. β3Gal-T1, -T2, and -T5 form Galβ1-3GlcNAc linkages (type 1 chain structures) in glycolipids and glycoproteins (Kolbinger et al. 1998; Amado et al. 1998; Hennet et al. 1998; Isshiki et al. 1999; Zhou et al. 1999a), β3Gal-T4 forms Galβ1-3GalNAc in gangliosides (Amado et al. 1998), β3Gal-T6 forms Galβ1-3Gal in the proteoglycan linker region (Bai et al. 2001), and C1Gal-T1 forms Galβ1-3GalNAca1-O-Ser/Thr (core 1 structure) in O-glycans (Ju et al. 2002). The acceptor molecules for these enzymes include glycosphingolipids, N-glycoproteins, mucin-type O-glycoproteins, and proteoglycans (Miyazaki et al. 1997; Amado et al. 1999).