Oxidation of iron(II) porphyrins by alkyl halides

Wade, Ruth S.; Castro, C. E.

doi:10.1021/ja00782a040

Cited by 147 publications

(99 citation statements)

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“…These studies showed that the reaction with alkyl halides proceeds via the formation of free radicals (2). The relatively high amount of CA formed by factor F430 in our study indicates that the dechlorination by factor F430 proceeds via a free radical, as proposed previously for reductive dehalogenation reactions catalyzed by iron(II) porphyrins (43). The exact mechanism and an explanation for the different ethylene to CA ratios found with native F430 or 12,13-di-epi-F430 remains to be elucidated.…”

Section: Discussionsupporting

confidence: 84%

Evidence for the involvement of corrinoids and factor F430 in the reductive dechlorination of 1,2-dichloroethane by Methanosarcina barkeri

et al. 1992

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Cobalamin and the native and diepimeric forms of factor F430 catalyzed the reductive dechlorination of 1,2-dichloroethane (1,2-DCA) to ethylene or chloroethane (CA) in a buffer with Ti(III) citrate as the electron donor. Ethylene was the major product in the cobalamin-catalyzed transformation, and the ratio of ethylene to CA formed was 25:1. Native F430 and 12,13-di-epi-F430 produced ethylene and CA in ratios of about 2:1 and 1:1, respectively. Cobalamin dechlorinated 1,2-DCA much faster than did factor F430. Dechlorination rates by all three catalysts showed a distinct pH dependence, correlated in a linear manner with the catalyst concentration and doubled with a temperature increase of 10°C. Crude and boiled cell extracts of Methanosarcina barkeri also dechlorinated 1,2-DCA to ethylene and CA with Ti(III) citrate as the reductant. The catalytic components in boiled extracts were heat and oxygen stable and had low molecular masses. Fractionation of boiled extracts by a hydrophobic interaction column revealed that part of the dechlorinating components had a hydrophilic and part had a hydrophobic character. These chemical properties of the dechlorinating components and spectral analysis of boiled extracts indicated that corrinoids or factor F430 was responsible for the dechlorinations. The ratios of 3:1 to 7:1 of ethylene and CA formed by cell extracts suggested that both cofactors were concomitantly active.Chlorinated aliphatic C1 and C2 hydrocarbons, widespread contaminants in different environments, are found to be reductively dechlorinated by pure cultures of methanogens, sulfate reducers, homoacetogens, and other anaerobic bacteria (4,11,13,16,18,22,26,33). Tetrachloromethane (CCd4) was found to be transformed to lower-chlorinated methanes and CO2 by native or autoclaved cell suspensions of methanogens, Acetobacterium woodii, and Desulfobacterium autotrophicum (12,13,26). These anaerobic bacteria fix CO2 via the acetyl-coenzyme A pathway (Wood pathway) or degrade acetate via a reversed acetyl-coenzyme A pathway (17,32,42,44). Carbon monoxide dehydrogenase and a corrinoid-iron-sulfur protein are central enzymes of this pathway. It has been suggested that the anaerobic transformation of CCl4 could be a cometabolic activity of Wood pathway enzymes (12, 13). Free cobalamin catalyzed reductive dechlorination of CCl4 in a buffer reduced with Ti(III) citrate as the electron donor (27). In addition to lowerchlorinated methanes, cobalamin produced CO from CCl4 (28), a compound which is oxidized to CO2 by carbon monoxide dehydrogenase (17,32,42,44). In methanogenic bacteria, factor F430 may also be involved in reductive dechlorination. Factor F430 is a cofactor of methyl-coenzyme M reductase, the enzyme which catalyzes the last step in methanogenesis from methyl-coenzyme M to CH4 (14). This cofactor reductively dechlorinated CCl4 to lower-chlorinated methanes (26). All Cell suspensions of methanogens reductively dechlorinated 1,2-dichloroethane (1,2-DCA) to ethylene and chloroethane (CA) (22). We demonstrate here th...

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Section: Discussionsupporting

confidence: 84%

Evidence for the involvement of corrinoids and factor F430 in the reductive dechlorination of 1,2-dichloroethane by Methanosarcina barkeri

et al. 1992

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“…This protein was purified and found to be involved in the reductive dechlorination of trichloronitromethane [10]. Earlier reports on reductive dehalogenating activity of iron(II) porphyrins [22], heine proteins [23], and reduced liver microsomes [24] already indicated that protein-bound iron(II) porphyrins were the catalysts of the observed dehalogenations by whole cells. Reductive dechlorination of tetrachloromethane by the iron-reducing bacterium Shewanella putrefaciens appears to be catalyzed by cytochromes produced upon microaerophilic growth [25].…”

Section: Alkyl Reductite Dechlorinationmentioning

confidence: 99%

Physiological meaning and potential for application of reductive dechlorination by anaerobic bacteria

Holliger

1994

FEMS Microbiology Reviews

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Abstract:The physiological meaning of reductive dechlorination reactions catalyzed by anaerobic bacteria can be explained as a co-metabolic activity or as a novel type of respiration. Co-metabolic activities have been found mainly with alkyl halides. They are non-specific reactions catalyzed by various enzyme systems of facultative as well as obligate anaerobic bacteria. In contrast, the reductive dechlorinations involved in metabolic respiration processes are very specific reactions. Only a limited number of alkyl and aryl chlorinated compounds is presently known to function as a terminal electron acceptor in a few, recently isolated bacteria. Metabolic dechlorination rates are in general several orders of magnitude higher than co-metabolic ones. Both reaction types are suitable for the anaerobic treatment of waste streams.

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“…Although a broad spectrum of products can be formed, all reductive dehalogenation reactions involve electron transfer to the halogenated substrate (Wade & Castro 1973;Vogel et al 1987;Criddle & McCarty 1991;Krone et al 1991). Therefore, the reaction rate can be affected by the concentrations of primary electron-donor and -acceptor substrates, which control the intracellular availability of electrons.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of a model for the effects of substrate interactions on the kinetics of reductive dehalogenation

Wrenn

Rittmann²

1996

Biodegradation

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The effects of primary electron-donor and electron-acceptor substrates on the kinetics of TCA biodegradation in sulfate-reducing and methanogenic biofilm reactors are presented. Of the common anaerobic electron-donor substrates that were tested, only formate stimulated the TCA biodegradation rate in both reactors. In the sulfatereducing reactor, glucose also stimulated the reaction rate. The effects of formate and sulfate on TCA biodegradation kinetics were analyzed using a model for primary substrate effects on reductive dehalogenation. Although some differences between the model and the data are evident, the observed responses of the TCA degradation rate to formate and sulfate were consistent with the model. Formate stimulated the TCA degradation rate in both reactors over the entire range of TCA concentrations that were studied (from 50 pg TCA/L to 100 mg TCA/L). The largest effects occurred at high TCA concentrations, where the dehalogenation kinetics were zero order. Sulfate inhibited the first-order TCA degradation rate in the sulfate-reducing reactor, but not in the methanogenic reactor. Molybdate, which is a selective inhibitor of sulfate reduction, stimulated the TCA removal rate in the sulfate-reducing reactor, but had no effect in the methanogenic reactor.

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Oxidation of iron(II) porphyrins by alkyl halides

Cited by 147 publications

References 1 publication

Evidence for the involvement of corrinoids and factor F430 in the reductive dechlorination of 1,2-dichloroethane by Methanosarcina barkeri

Evidence for the involvement of corrinoids and factor F430 in the reductive dechlorination of 1,2-dichloroethane by Methanosarcina barkeri

Physiological meaning and potential for application of reductive dechlorination by anaerobic bacteria

Evaluation of a model for the effects of substrate interactions on the kinetics of reductive dehalogenation

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