α-N-acetylgalactosaminide α-2,6-sialyltransferase

α-N-Acetylgalactosamine linked to threonine or serine is also an acceptor, when substituted at the 3-position. Reaction: CMP-N-acetylneuraminate + glycano-(1→3)-(N-acetyl-α-D-galactosaminyl)-glycoprotein = CMP + glycano-[(2→6)-α-N-acetylneuraminyl]-(N-acetyl-D-galactosaminyl)-glycoprotein