Bilirubin monoglucuronide is conjugated to bilirubin diglucuronide Authored: Jassal, B, 2005-02-23 15:02:50 EC Number: 2.4.1.17 Edited: Jassal, B, 2010-05-27 Pubmed3082969 Pubmed4639028 Pubmed6654901 Pubmed6796486 Reactome Database ID Release 43159179 Reactome, http://www.reactome.org ReactomeREACT_22319 Reviewed: D'Eustachio, P, 2010-05-08 The principal conjugate of bilirubin in bile is bilirubin diglucuronide. The monmeric form of UGT1A1 (Bilirubin UDP-glucuronyltransferase) only conjugates the first step of bilirubin conjugation to form the monoglucuronide. A tetrameric form of UGT1A1 can convert bilirubin to both the monoglucuronide and the diglucuronide. bilirubin monoglucuronide + UDP-glucuronic acid => bilirubin diglucuronide + UDP