alpha-N-acetylneuraminide alpha-2,8-sialyltransferase 6 (also known as alpha-2,8-sialyltransferase 8F) prefers O-glycans to N-glycans or glycolipids as acceptor substrates. ST8Sia family members are alpha-N-acetylneuraminide alpha-2,8-sialyltransferases that catalyze an alpha-2,8-linkage between sialic acid and the terminal sialic acid residues of glycochains, by transfering sialic acid from CMP-Sia. The ST8Sia family belongs to glycosyltransferase family 29(GT29).