PMID- 35467338
OWN - NLM
STAT- MEDLINE
DCOM- 20220519
LR  - 20220724
IS  - 1520-5851 (Electronic)
IS  - 0013-936X (Linking)
VI  - 56
IP  - 10
DP  - 2022 May 17
TI  - Exploring Mechanisms of Biotic Chlorinated Alkane Reduction: Evidence of 
      Nucleophilic Substitution (S(N)2) with Vitamin B(12).
PG  - 6325-6336
LID - 10.1021/acs.est.1c06066 [doi]
AB  - Chlorinated alkanes are notorious groundwater contaminants. Their natural 
      reductive dechlorination by microorganisms involves reductive dehalogenases 
      (RDases) containing cobamide as a cofactor. However, underlying mechanisms of 
      reductive dehalogenation have remained uncertain. Here, observed products, 
      radical trap experiments, UV-vis, and mass spectra demonstrate that (i) reduction 
      by cobalamin (vitamin B(12)) involved chloroalkyl-cobalamin complexes (ii) whose 
      formation involved a second-order nucleophilic substitution (S(N)2). Dual element 
      isotope analysis subsequently linked insights from our model system to microbial 
      reductive dehalogenation. Identical observed isotope effects in reduction of 
      trichloromethane by Dehalobacter CF and cobalamin (Dehalobacter CF, epsilon(C) = -27.9 
      +/- 1.7 per thousand; epsilon(Cl) = -4.2 +/- 0. per thousand; lambda = 6.6 +/- 0.1; cobalamin, epsilon(C) = -26.0 +/- 0.9 per thousand; epsilon(Cl) 
      = -4.0 +/- 0.2 per thousand; lambda = 6.5 +/- 0.2) indicated the same underlying mechanism, as did 
      identical isotope effects in the reduction of 1,2-dichloroethane by 
      Dehalococcoides and cobalamin (Dehalococcoides, epsilon(C) = -33.0 +/- 0.4 per thousand; epsilon(Cl) = -5.1 
      +/- 0.1 per thousand; lambda = 6.5 +/- 0.2; cobalamin, epsilon(C) = -32.8 +/- 1.7 per thousand; epsilon(Cl) = -5.1 +/- 0.2 per thousand; lambda = 
      6.4 +/- 0.2). In contrast, a different, non-S(N)2 reaction was evidenced by 
      different isotope effects in reaction of 1,2-dichloroethane with Dehalogenimonas 
      (epsilon(C) = -23.0 +/- 2.0 per thousand; epsilon(Cl) = -12.0 +/- 0.8 per thousand; lambda = 1.9 +/- 0.02) illustrating a 
      diversity of biochemical reaction mechanisms manifested even within the same 
      class of enzymes (RDases). This study resolves open questions in our 
      understanding of bacterial reductive dehalogenation and, thereby, provides 
      important information on the biochemistry of bioremediation.
FAU - Heckel, Benjamin
AU  - Heckel B
AD  - Chair of Analytical Chemistry and Water Chemistry, Technical University of 
      Munich, Lichtenbergstr. 4, 85748 Garching, Germany.
FAU - Elsner, Martin
AU  - Elsner M
AUID- ORCID: 0000-0003-4746-9052
AD  - Chair of Analytical Chemistry and Water Chemistry, Technical University of 
      Munich, Lichtenbergstr. 4, 85748 Garching, Germany.
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
DEP - 20220425
PL  - United States
TA  - Environ Sci Technol
JT  - Environmental science & technology
JID - 0213155
RN  - 0 (Alkanes)
RN  - 0 (Carbon Isotopes)
RN  - 0 (Vitamins)
RN  - P6YC3EG204 (Vitamin B 12)
SB  - IM
MH  - Alkanes
MH  - Biodegradation, Environmental
MH  - Carbon Isotopes
MH  - *Groundwater
MH  - *Vitamin B 12/analysis
MH  - Vitamins/analysis
OTO - NOTNLM
OT  - biodegradation
OT  - chlorinated alkanes
OT  - compound-specific isotope analysis
OT  - groundwater contamination
OT  - vitamin B12
EDAT- 2022/04/26 06:00
MHDA- 2022/05/20 06:00
CRDT- 2022/04/25 12:28
PHST- 2022/04/26 06:00 [pubmed]
PHST- 2022/05/20 06:00 [medline]
PHST- 2022/04/25 12:28 [entrez]
AID - 10.1021/acs.est.1c06066 [doi]
PST - ppublish
SO  - Environ Sci Technol. 2022 May 17;56(10):6325-6336. doi: 10.1021/acs.est.1c06066. 
      Epub 2022 Apr 25.