Addition of GlcNAc to the glycan on the A arm Authored: Dall'Olio, GM, 2009-11-10 EC Number: 2.4.1.101 Edited: Jassal, B, 2010-09-17 Pubmed1702225 Pubmed1827260 Reactome Database ID Release 43964768 Reactome, http://www.reactome.org ReactomeREACT_25236 Reviewed: Gagneux, P, 2010-11-18 This is the first committed step in the synthesis of complex and hybrid N-glycans and is specific to multicellular organisms (Kumar et al, 1990; Hull et al, 1991). Hybri N-glycans are important for inter-cellular interactions and therefore during embryonic development of multicellular organisms, and it is probable that these pathways have evolved just before the emergence of multicellular organisms. Support for this hypothesis is provided by the phenomena of CDG and by the effects of null mutations in C.elegans.