The function of Ensembl gene identifier ENSG00000136840 (ST6GALNAC4, ST6 N-acetylgalactosaminide alpha-2,6-sialyltransferase 4) is as follows. Transfers the sialyl group (N-acetyl-alpha-neuraminyl or NeuAc) from CMP-NeuAc to the GalNAc residue on the NeuAc-alpha-2,3-Gal- beta-1,3-GalNAc sequence of glycoproteins and glycolipids forming an alpha-2,6-linkage. Produces branched type disialyl structures by transfer of a sialyl group onto a GalNAc residue inside the backbone core chains. Prefers O-glycans to glycoproteins or glycolipids. .