Addition of the sixth mannose to the N-glycan precursor by ALG3. Authored: Dall'Olio, GM, 2009-11-10 Edited: Jassal, B, 2009-11-10 Pubmed12200473 Pubmed15840742 Reactome Database ID Release 43446188 Reactome, http://www.reactome.org ReactomeREACT_22415 Reviewed: Gagneux, P, 2010-04-16 The sixth mannose is added to the N-glycan precursor. This reaction occurs in the ER lumen and uses a different mannose donor (dolichyl phosphate D-mannose) than the previous steps. It has been proposed that ALG3, along with all the mannosyl- and glucosyl transferases in the N-glycan biosynthesis pathway that use dolichyl phosphate D-mannose or dolichyl phosphate D-glucose as donor, derive from duplications of a common ancestral enzyme (Oriol R et al, 2002). Defects in ALG3 are associated with Congenital Disorder of Glycosylation 1D (CDG1D) (Sun L et al, 2005).