5cts
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PROPOSED MECHANISM FOR THE CONDENSATION REACTION OF CITRATE SYNTHASE. 1.9-ANGSTROMS STRUCTURE OF THE TERNARY COMPLEX WITH OXALOACETATE AND CARBOXYMETHYL COENZYME A
OverviewOverview
The crystal structure of the ternary complex citrate synthase-oxaloacetate-carboxymethyl coenzyme A has been solved to a resolution of 1.9 A and refined to a conventional crystallographic R factor of 0.185. The structure resembles a proposed transition state of the condensation reaction and suggests that the condensation reaction proceeds through a neutral enol rather than an enolate intermediate. A mechanism for the condensation reaction is proposed which involves the participation of three key catalytic groups (Asp 375, His 274, and His 320) in two distinct steps. The proposed mechanism invokes concerted general acid-base catalysis twice to explain both the energetics of the reaction and the experimentally observed inversion of stereochemistry at the attacking carbon atom.
About this StructureAbout this Structure
5CTS is a Single protein structure of sequence from Gallus gallus with and as ligands. Active as Citrate (Si)-synthase, with EC number 2.3.3.1 Full crystallographic information is available from OCA.
ReferenceReference
Proposed mechanism for the condensation reaction of citrate synthase: 1.9-A structure of the ternary complex with oxaloacetate and carboxymethyl coenzyme A., Karpusas M, Branchaud B, Remington SJ, Biochemistry. 1990 Mar 6;29(9):2213-9. PMID:2337600
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