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Insight into the Mechanism Underlying Dehalococcoides mccartyi Strain CBDB1-Mediated B 12 -Dependent Aromatic Reductive Dehalogenation.
- Source :
-
Environmental science & technology [Environ Sci Technol] 2023 Jul 25; Vol. 57 (29), pp. 10773-10781. Date of Electronic Publication: 2023 Jul 10. - Publication Year :
- 2023
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Abstract
- Anaerobic bacteria transform aromatic halides through reductive dehalogenation. This dehalorespiration is catalyzed by the supernucleophilic coenzyme vitamin B <subscript>12</subscript> , cob(I)alamin, in reductive dehalogenases. So far, the underlying inner-sphere electron transfer (ET) mechanism has been discussed controversially. In the present study, all 36 chloro-, bromo-, and fluorobenzenes and full-size cobalamin are analyzed at the quantum chemical density functional theory level with respect to a wide range of theoretically possible inner-sphere ET mechanisms. The calculated reaction free energies within the framework of Co <superscript>I</superscript> ···X (X = F, Cl, and Br) attack rule out most of the inner-sphere pathways. The only route with feasible energetics is a proton-coupled two-ET mechanism that involves a B <subscript>12</subscript> side-chain tyrosine (modeled by phenol) as a proton donor. For 12 chlorobenzenes and 9 bromobenzenes with experimental data from Dehalococcoides mccartyi strain CBDB1, the newly proposed PC-TET mechanism successfully discriminates 16 of 17 active from 4 inactive substrates and correctly predicts the observed regiospecificity to 100%. Moreover, fluorobenzenes are predicted to be recalcitrant in agreement with experimental findings. Conceptually, based on the Bell-Evans-Polanyi principle, the computational approach provides novel mechanistic insights and may serve as a tool for predicting the energetic feasibility of reductive aromatic dehalogenation.
Details
- Language :
- English
- ISSN :
- 1520-5851
- Volume :
- 57
- Issue :
- 29
- Database :
- MEDLINE
- Journal :
- Environmental science & technology
- Publication Type :
- Academic Journal
- Accession number :
- 37428517
- Full Text :
- https://doi.org/10.1021/acs.est.3c00364