Evolution of function in the crotonase superfamily: the stereochemical course of the reaction catalyzed by 2-ketocyclohexanecarboxyl-CoA hydrolase |
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Authors: | Eberhard Ellen D Gerlt John A |
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Institution: | Department of Biochemistry, University of Illinois, Urbana, Illinois 61801, USA. |
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Abstract: | Members of the mechanistically diverse enoyl-CoA hydratase (crotonase) superfamily catalyze reactions that involve stabilization of an enolate anion derived from an acyl thioester of coenzyme A. 2-Ketocyclohexanecarboxyl-CoA hydrolase (BadI), found in a pathway for anaerobic degradation of benzoate by Rhodopseudomonas palustris, is a member of the crotonase superfamily that catalyzes a reverse Dieckmann reaction in which the substrate is hydrolyzed to pimelyl-CoA. The substrate is the configurationally labile 2S-ketocyclohexanecarboxyl-CoA, and in 2H2O solvent hydrogen is incorporated into the 2-proS position of the pimelyl-CoA product. Therefore, the stereochemical course of the BadI-catalyzed reaction is inversion. This information is important for understanding the roles of active-site functional groups in the active site of BadI as well as in the active sites of the homologous 1,4-dihydroxynaphthoyl-CoA synthases that catalyze a forward Dieckmann reaction. |
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