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Title (Primary) Dehalococcoides-mediated B12-dependent reductive dehalogenation of aromatics does not proceed through outer-sphere electron transfer
Author Zhang, S.; Adrian, L.; Schüürmann, G.
Journal Environmental Science & Technology
Year 2020
Department OEC; UBT
Volume 54
Issue 24
Page From 15751
Page To 15758
Language englisch
Supplements https://pubs.acs.org/doi/suppl/10.1021/acs.est.0c04404/suppl_file/es0c04404_si_001.pdf
Abstract Several anaerobic bacteria can couple the reduction of aromatic halides to energy conservation. This organohalide respiration is catalyzed by enzymes containing cob(I)alamin, an activated supernucleophilic form of the coenzyme vitamin B12. However, the mechanism underlying the electron transfer (inner-sphere vs outer-sphere ET) still remains elusive. To clarify this issue, we selected 36 fluoro-, chloro-, and bromobenzenes as representative substrates and calculated their free-energy barriers at the quantum chemical density functional theory level, considering a wide range of theoretically possible outer-sphere ET mechanisms. Across all 336 reaction routes addressed, 334 routes involve free-energy barriers larger than 20 kcal/mol. For two reaction routes with highly brominated benzenes, free-energy barriers below 20 kcal/mol imply abiotic reduction as observed in experiments. Thus, microbial B12-dependent aromatic reductive dehalogenation does not proceed through an outer-sphere ET mechanism. Instead, the present study strongly suggests that microbe-catalyzed reductive dehalogenation of aromatic halides is governed by inner-sphere ET.
Persistent UFZ Identifier https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=24163
Zhang, S., Adrian, L., Schüürmann, G. (2020):
Dehalococcoides-mediated B12-dependent reductive dehalogenation of aromatics does not proceed through outer-sphere electron transfer
Environ. Sci. Technol. 54 (24), 15751 - 15758