ST6GalNAc family members are alpha-N-acetylgalactosaminide alpha-2,6-sialyltransferases that catalyze an alpha-2,6-linkage between sialic acid and the N-acetylgalactosamine residues of glycochains through an 2,6-linkage, by transfering sialic acid from CMP-Sia. ST6GalNAc3, 4, 5, and 6 utilizeSia2,3Galbeta1,3GalNAc as an acceptor with different individual substrate specificities. The ST6GalNac family belongs to glycosyltransferase family 29 (GT29).