Keratan(4)-PG Keratan(3)-PG The keratan chain can be capped by N-acetylneuraminic acid Authored: Jassal, B, 2011-12-01 EC Number: 2.4.99.4 Edited: Jassal, B, 2011-12-01 Pubmed10206952 Pubmed10504389 Pubmed8333853 Pubmed8611500 Pubmed8920913 Reactome Database ID Release 432046285 Reactome, http://www.reactome.org ReactomeREACT_121285 Reviewed: D'Eustachio, P, 2012-03-28 The human genes ST3GAL1-4 and 6 encode for sialyltransferase1-4 and 6 respectively (Shang et al. 1999, Kim et al. 1996, Kitagawa and Paulson, 1993, Basu et al. 1993, Okajima et al. 1999). They add a sialyl residue to the growing keratan chain, blocking any further chain elongation.