Mucins Tn antigens Addition of GalNAc to mucins to form the Tn antigen Authored: Jassal, B, 2010-07-19 EC Number: 2.4.1.41 Edited: Jassal, B, 2010-07-19 Pubmed12464682 Pubmed9295285 Pubmed9394011 Reactome Database ID Release 43913675 Reactome, http://www.reactome.org ReactomeREACT_115586 Reviewed: Ferrer, A, 2011-11-04 The family of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferases (GalNAc-transferases, GALNTs) carry out the addition of N-acetylgalactosamine on serine or threonine residues of proteins, especially mucins (Wandall et al, 1997). This reaction takes place in the Golgi apparatus (Röttger et al, 1998). There are 20 members of the GALNTs, 15 of which have been characterised and 5 candidate members which are thought to belong to this family based on sequence similarity. The molecular chaperone C1GALT1-specific chaperone (COSMC) is thought to be required for N-acetylgalactosaminyltransferase activity (Yu and Cummings, 2002).