The function of GAL3ST4 (galactose-3-O-sulfotransferase 4, Ensembl gene identifier ENSG00000197093) is as follows. Catalyzes the transfer of a sulfate group from 3'- phosphoadenylyl sulfate (PAPS) to the C-3 hydroxyl group of terminal non-reducing beta-1,3-linked galactose residues, exclusively in O- linked glycoproteins (PubMed:11333265, PubMed:14701868). Participates in galactose sulfation and acts on core 1 (Gal-beta-1,3-GalNAc-R) structures (PubMed:11333265, PubMed:14701868). In vitro, also recognizes Gal-beta-1,3 (GlcNAc-beta-1,6)GalNAc-R, asialofetuin, the Globo H precursor and Gal-beta-1,3(6-O-sulfo)GalNAc-R structures as good substrates (PubMed:11333265, PubMed:14701868). .