doi:10.1042/BCJ20180172engRaimi, O.G.Hurtado-Guerrero, R.Van Aalten, D.M.F.Evidence for substrate-assisted catalysis in N-acetylphosphoglucosamine mutaseART-2018-107715N-acetylphosphoglucosamine mutase (AGM1) is a key component of the hexosamine biosynthetic pathway that produces UDP-GlcNAc, an essential precursor for a wide range of glycans in eukaryotes. AGM belongs to the a-D-phosphohexomutase metalloenzyme superfamily and catalyzes the interconversion of N-acetylglucosamine-6-phosphate (GlcNAc-6P) to N-acetylglucosamine-1-phosphate (GlcNAc-1P) through N-acetylglucosa-mine-1, 6-bisphosphate (GlcNAc-1, 6-bisP) as the catalytic intermediate. Although there is an understanding of the phosphoserine-dependent catalytic mechanism at enzymatic and structural level, the identity of the requisite catalytic base in AGM1/phosphoglucomu-tases is as yet unknown. Here, we present crystal structures of a Michaelis complex of AGM1 with GlcNAc-6P and Mg2+, and a complex of the inactive Ser69Ala mutant together with glucose-1, 6-bisphosphate (Glc-1, 6-bisP) that represents key snapshots along the reaction co-ordinate. Together with mutagenesis, these structures reveal that the phosphate group of the hexose-1, 6-bisP intermediate may act as the catalytic base.2018http://zaguan.unizar.es/record/7492010.1042/BCJ20180172http://zaguan.unizar.es/record/74920oai:zaguan.unizar.es:74920BIOCHEMICAL JOURNAL 475, 15 (2018), 2547-2557byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess