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Stack TMM, Li W, Johnson WH, Zhang YJ, Whitman CP. Inactivation of 4-Oxalocrotonate Tautomerase by 5-Halo-2-hydroxy-2,4-pentadienoates. Biochemistry 2018; 57:1012-1021. [PMID: 29303557 DOI: 10.1021/acs.biochem.7b00899] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
5-Halo-2-hydroxy-2,4-pentadienoates (5-halo-HPDs) are reportedly generated in the bacterial catabolism of halogenated aromatic hydrocarbons by the meta-fission pathway. The 5-halo-HPDs, where the halogen can be bromide, chloride, or fluoride, result in the irreversible inactivation of 4-oxalocrotonate tautomerase (4-OT), which precedes the enzyme that generates them. The loss of activity is due to the covalent modification of the nucleophilic amino-terminal proline. Mass spectral and crystallographic analysis of the modified enzymes indicates that inactivation of 4-OT by 5-chloro- and 5-bromo-2-hydroxy-2,4-pentadienoate follows a mechanism different from that for the inactivation of 4-OT by 5-fluoro-2-hydroxy-2,4-pentadienoate. The 5-chloro and 5-bromo derivatives undergo 4-OT-catalyzed tautomerization to their respective α,β-unsaturated ketones followed by attack at C5 (by the prolyl nitrogen) with concomitant loss of the halide. For the 5-fluoro species, the presence of a small amount of the α,β-unsaturated ketone could result in a Michael addition of the prolyl nitrogen to C4 followed by protonation at C3. The fluoride is not eliminated. These observations suggest that the inactivation of 4-OT by a downstream metabolite could hamper the efficacy of the pathway, which is the first time that such a bottleneck has been reported for the meta-fission pathway.
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Affiliation(s)
- Tyler M M Stack
- Department of Molecular Biosciences, The University of Texas at Austin , Austin, Texas 78712, United States.,Institute for Cellular and Molecular Biology, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Wenzong Li
- Department of Molecular Biosciences, The University of Texas at Austin , Austin, Texas 78712, United States.,Institute for Cellular and Molecular Biology, The University of Texas at Austin , Austin, Texas 78712, United States
| | - William H Johnson
- Division of Chemical Biology and Medicinal Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Yan Jessie Zhang
- Department of Molecular Biosciences, The University of Texas at Austin , Austin, Texas 78712, United States.,Institute for Cellular and Molecular Biology, The University of Texas at Austin , Austin, Texas 78712, United States
| | - Christian P Whitman
- Division of Chemical Biology and Medicinal Chemistry, The University of Texas at Austin , Austin, Texas 78712, United States
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