4.2.99.20 | 5-enolpyruvoyl-6-hydroxy-2-succinylcyclohex-3-ene-1-carboxylate = (1R,6R)-6-hydroxy-2-succinylcyclohexa-2,4-diene-1-carboxylate + pyruvate |
the nucleophilicity of the catalyitc serine-histidine-aspartate triad is shielded and its catalytic role is limited to being a specific general base by an open-closed conformational change. The enzyme adopts an open conformation without a functional triad in its ligand-free form and a closed conformation with a fully functional catalytic triad in the presence of its reaction product. The open-to-closed conformational transition involves movement of half of the alpha-helical cap domain, which causes extensive structural changes in the apha/beta-domain and forces the side chainof the triad histidine to adopt an energetically disfavored gauche conformation to form the functional triad. The inactive open conformation without a triad prevails in ligand-free solution and is converted to the closed conformation with a properly formed triad by the reaction product |
730042 |