Sia-alpha-2,3-Gal-beta-1,4-GlcNAc-R:alpha 2,8-sialyltransferase (St8sia3)

Catalyzes the transfer of sialic acid from a CMP-linked sialic acid donor on the terminal sialic acid of an acceptor through alpha-2,8-linkages. Is active with alpha-2,3-connected, alpha-2,6-linked and alpha-2,8-linked sialic acid of N-linked oligosaccharides of glycoproteins and glycolipids.

Shows preference for substrates with alpha-2,3-linked terminal sialic acid. It can form polysialic acid in vitro right on alpha-2,3-, alpha-2,6-, or alpha-2,8-linked sialic acid.