5.4.99.5 Chorismate = prephenate - - 5.4.99.5 Chorismate = prephenate Three active sites are formed in the interstices between three subunits. Each active site is composed of the residues of two adjacent subunits. The two Arg hold the chorismate. Crucial distance between Arg6 and Arg63* controls the conformation of the chorismate. The residues in the close vicinity to the chorismate substrate are Arg6, Glu77, Arg89, Tyr 107, Leu114, and Arg115 from one subunit and Phe57*, Ala59*, Arg63*, Leu72*, and Leu73* from the other subunit. The family of the chorismate mutase enzymes shares a common E.S active site 672198 5.4.99.5 Chorismate = prephenate the active site is formed within a single chain without any contribution from the second chain in a dimer -, 674312 5.4.99.5 Chorismate = prephenate CMs are extremly versatile enzymes and can be structurally divided into two major groups: the type I or AroH class, which comprises CMs characterized by a trimericpseudo alpha/beta-barrel structure, and the type II or AroQ class, which comprises CMs can also be monofunctional, bifunctional (generally fused to another shikimate pathway member), exported, and/or allosterically regulated 674346 5.4.99.5 Chorismate = prephenate CMs are extremly versatile enzymes and can be strucurally divided into two major groups: the type I or AroH class, which comprises CMs characterized by a trimericpseudo alpha/beta-barrel structure, and the type II or AroQ class, which comprises CMs, can also be monofunctional, bifunctional (generally fused to another shikimate pathway member), exported, and/or allosterically regulated 674346 5.4.99.5 Chorismate = prephenate Wild-type-reaction: Arg63, Arg116, Arg7, and Tyr108 required for the relative orientation of the substrate at the active site, the structural rearrangement in the Glu78-Arg90-substrate controls the strength of the hydrogen bonds. The hydrogen bonds connecting the Glu78-Arg90-substrate cooperatively control the stability of TS relative to the ES complex and the positive charge on Arg90 polarizes the substrate in the TS region to gain more electrostatic stabilization. Method: electron quantum chemical calculations by fragment molecular orbital (FMO) method. The structural refinement and reaction path search are performed by the ab initio QM/MM treatment. Usage of the AMBER standard parameter set (parm.96) for the MM force-field calculations. Reaction path search: On the basis of the gas-phase IRC (intrinsic reaction coordinate) profile of chorismate isomerization, the linear reaction path is calculated first 675611 5.4.99.5 Chorismate = prephenate The active site of the enzyme which is found in a pocket formed by two different chains is shown. Applying the TPS method of Chandler and co-workers to study the chorismate to prephenate reaction 675620 5.4.99.5 Chorismate = prephenate via near attack conformation and transition state intermediates, reaction mechanism, overview 726963 5.4.99.5 Chorismate = prephenate the enzyme catalyzes the conversion of chorismate to prephenate, which is formally a Claisen rearrangement that proceeds via an endo-oxabicyclic transition state with a chair-like geometry 748301 5.4.99.5 Chorismate = prephenate catalytic reaction mechanism, role of conformational dynamics and entropies in enzyme catalysis, overview. Large-scale conformational dynamics make important catalytic contributions to sampling conformational regions in favor of binding the transition state of substrate 749298