OGT is a nucleocytoplasmic glycosyltransferase (uridine diphospho-N--acetylglucosamine:polypeptide β-N-acetylglucosaminyltransferase or O-GlcNAc transferase) assigned to the GT41 family in the CAZY (Carbohydrate-Active enZYme) database. Using UDP-GlcNAc Disodium Salt (UDP-GlcNAc) as the donor substrate, this enzyme modifies thousands of proteins by adding a unique N-acetylglucosamine residue onto acceptor substrates mainly confined within cytosol and nucleus.