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Publication Abstract from PubMed

Pathogenic bacteria are endowed with an arsenal of specialized enzymes to convert nutrient compounds from their cell hosts. The essential N-acetylmannosamine-6-phosphate 2-epimerase (NanE) belongs to a convergent glycolytic pathway for utilization of the three amino sugars, GlcNAc, ManNAc and sialic acid. The crystal structure of ligand-free NanE from Clostridium perfringens reveals a modified TIM (beta/alpha)8 barrel in which a stable dimer is formed by exchanging the C-terminal helix. By retaining catalytic activity in the crystalline state, the structure of the enzyme bound to the GlcNAc-6P product identifies the topology of the active site pocket and points to invariant residues Lys66 as a putative single catalyst, supported by the structure of the (catalytically inactive) Lys66Ala mutant in complex with substrate ManNAc-6P. 1H-NMR-based time course assays of native NanE and mutated variants demonstrate the essential role of Lys66 for the epimerization reaction with participation of neighboring Arg43, Asp126 and Glu180 residues. These findings unveil a one-base catalytic mechanism of C2 deprotonation/reprotonation via an enolate intermediate and provide the structural basis for the development of new antimicrobial agents against this family of bacterial 2-epimerases.

Structural and functional characterization of the Clostridium perfringens N-acetylmannosamine-6-phosphate 2-epimerase essential for the sialic acid salvage pathway.,Pelissier MC, Sebban-Kreuzer C, Guerlesquin F, Brannigan JA, Bourne Y, Vincent F J Biol Chem. 2014 Oct 15. pii: jbc.M114.604272. PMID:25320079^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.