Conversion of <i>cis</i>‐2‐carboxycyclohexylacetyl‐CoA in the downstream pathway of anaerobic naphthalene degradation

Weyrauch, Philip; Zaytsev, Andrey V.; Stephan, Susanne; Kocks, Lena; Schmitz, Oliver J.; Golding, Bernard T.

doi:10.1111/1462-2920.13806

Cited by 17 publications

(10 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The remaining aromatic ring I of the naphthalene skeleton is then reduced, most likely to hexahydronaphthoyl‐CoA, followed by beta‐oxidation like reactions and ring cleavage. The downstream degradation pathway proceeds via cyclohexane derivatives (Weyrauch et al ., ) and the central metabolism is reached via pimeloyl‐CoA after the second ring cleavage (Weyrauch et al ., ).…”

Section: Introductionmentioning

confidence: 99%

Anaerobic degradation of phenanthrene by a sulfate‐reducing enrichment culture

Himmelberg

Brüls

Farmani

et al. 2018

Environmental Microbiology

Self Cite

View full text Add to dashboard Cite

Anaerobic degradation processes are very important to attenuate polycyclic aromatic hydrocarbons (PAHs) in saturated, anoxic sediments. However, PAHs are poorly degradable, leading to very slow microbial growth and thus resulting in only a few cultures that have been enriched and studied so far. Here, we report on a new phenanthrene-degrading, sulfate-reducing enrichment culture, TRIP1. Genome-resolved metagenomics and strain specific cell counting with FISH and flow cytometry indicated that the culture is dominated by a microorganism belonging to the Desulfobacteraceae family (60% of the community) and sharing 93% 16S rRNA sequence similarity to the naphthalene-degrading, sulfate-reducing strain NaphS2. The anaerobic degradation pathway was studied by metabolite analyses and revealed phenanthroic acid as the major intermediate consistent with carboxylation as the initial activation reaction. Further reduced metabolites were indicative of a stepwise reduction of the ring system. We were able to measure the presumed second enzyme reaction in the pathway, phenanthroate-CoA ligase, in crude cell extracts. The reaction was specific for 2-phenanthroic acid and did not transform other isomers. The present study provides first insights into the anaerobic degradation pathways of three-ringed PAHs. The biochemical strategy follows principles known from anaerobic naphthalene degradation, including carboxylation and reduction of the aromatic ring system.

show abstract

Section: Introductionmentioning

confidence: 99%

Anaerobic degradation of phenanthrene by a sulfate‐reducing enrichment culture

Himmelberg

Brüls

Farmani

et al. 2018

Environmental Microbiology

Self Cite

View full text Add to dashboard Cite

show abstract

“…7) by comparison with a chemically synthesized reference. This compound was previously identified as an intermediate in anaerobic naphthalene degradation and a downstream degradation pathway starting from this metabolite was recently described (1,8).…”

Section: Resultsmentioning

confidence: 97%

“…The downstream degradation pathway of naphthalene, which can serve as an exemplar for polycyclic aromatic hydrocarbons, does not proceed via benzoyl-CoA, but via metabolites with a cyclohexane skeleton (8). Our research aimed to elucidate the pathway further and to close the gap between the THNCoA reductase and the recently described downstream pathway starting from 2-carboxycyclohexylacetyl-CoA (1).…”

Section: Introductionmentioning

confidence: 99%

The 5,6,7,8-Tetrahydro-2-Naphthoyl-Coenzyme A Reductase Reaction in the Anaerobic Degradation of Naphthalene and Identification of Downstream Metabolites

Weyrauch

Heker

Zaytsev

et al. 2020

Appl Environ Microbiol

Self Cite

View full text Add to dashboard Cite

Anaerobic degradation of polycyclic aromatic hydrocarbons has been investigated mostly with naphthalene as a model compound. Naphthalene degradation by sulfate-reducing bacteria proceeds via carboxylation to 2-naphthoic acid, formation of a coenzyme A thioester, and subsequent reduction to 5,6,7,8-tetrahydro-2-naphthoyl-coenzyme A (THNCoA), which is further reduced to hexahydro-2-naphthoyl-CoA (HHNCoA) by tetrahydronaphthoyl-CoA reductase (THNCoA reductase), an enzyme similar to class I benzoyl-CoA reductases. When analyzing THNCoA reductase assays with crude cell extracts and NADH as electron donor via liquid chromatography-mass spectrometry (LC-MS), scanning for putative metabolites, we found that small amounts of the product of an HHNCoA hydratase were formed in the assays, but the downstream conversion by an NAD+-dependent β-hydroxyacyl-CoA dehydrogenase was prevented by the excess of NADH in those assays. Experiments with alternative electron donors indicated that 2-oxoglutarate can serve as an indirect electron donor for the THNCoA-reducing system via a 2-oxoglutarate:ferredoxin oxidoreductase. With 2-oxoglutarate as electron donor, THNCoA was completely converted and further metabolites resulting from subsequent β-oxidation-like reactions and hydrolytic ring cleavage were detected. These metabolites indicate a downstream pathway with water addition to HHNCoA and ring fission via a hydrolase acting on a β’-hydroxy-β-oxo-decahydro-2-naphthoyl-CoA intermediate. Formation of the downstream intermediate cis-2-carboxycyclohexylacetyl-CoA, which is the substrate for the previously described lower degradation pathway leading to the central metabolism, completes the anaerobic degradation pathway of naphthalene. IMPORTANCE Anaerobic degradation of polycyclic aromatic hydrocarbons is poorly investigated despite its significance in anoxic sediments. Using alternative electron donors for the 5,6,7,8-tetrahydro-2-naphthoyl-CoA reductase reaction, we observed intermediary metabolites of anaerobic naphthalene degradation via in vitro enzyme assays with cell extracts of anaerobic naphthalene degraders. The identified metabolites provide evidence that ring reduction terminates at the stage of hexahydro-2-naphthoyl-CoA and a sequence of β-oxidation-like degradation reactions starts with a hydratase acting on this intermediate. The final product of this reaction sequence was identified as cis-2-carboxycyclohexylacetyl-CoA, a compound for which a further downstream degradation pathway has recently been published (P. Weyrauch, A. V. Zaytsev, S. Stephan, L. Kocks, et al., Environ Microbiol 19:2819–2830, 2017, https://doi.org/10.1111/1462-2920.13806). Our study reveals the first ring-cleaving reaction in the anaerobic naphthalene degradation pathway. It closes the gap between the reduction of the first ring of 2-naphthoyl-CoA by 2-napthoyl-CoA reductase and the lower degradation pathway starting from cis-2-carboxycyclohexylacetyl-CoA, where the second ring cleavage takes place.

show abstract

“…Subsequent processing, which has been studied in a highly enriched freshwater sulfate‐reducing bacterium (strain N47) occurs via thioesterification to 2‐naphthoyl‐CoA, reduction of the distal ring to [5,6,7,8]‐tetrahydro‐2‐naphthoyl‐CoA (Eberlein et al ., 2013a; Eberlein et al ., 2013b; Estelmann et al ., 2015), and further reduction to hexahydro‐2‐naphthoyl‐CoA (Eberlein et al ., 2013b). Ring opening and beta‐oxidation converts the latter via pimeloyl‐CoA and glutaconyl‐CoA to acetyl‐CoA (Weyrauch et al ., 2017) that is oxidized to CO 2 via the CO‐dehydrogenase (oxidative Wood‐Ljungdahl, C 1 pathway Galushko et al ., 1999; Musat et al ., 2009).…”

Section: Introductionmentioning

confidence: 99%

Effect of energy deprivation on metabolite release by anaerobic marine naphthalene‐degrading sulfate‐reducing bacteria

Gao

Widdel

Musat

2020

Environmental Microbiology

View full text Add to dashboard Cite

The aromatic hydrocarbon naphthalene, which occurs in coal and oil, can be degraded by aerobic or anaerobic microorganisms. A widespread electron acceptor for the latter is sulfate. Evidence for in situ naphthalene degradation stems in particular from the detection of 2-naphthoate and [5,6,7,8]-tetrahydro-2-naphthoate in oil field samples. Because such intermediates are usually not detected in laboratory cultures with high sulfate concentrations, one may suppose that conditions in reservoirs, such as sulfate limitation, trigger metabolite release. Indeed, if naphthalene-grown cells of marine sulfate-reducing Deltaproteobacteria (strains NaphS2, NaphS3 and NaphS6) were transferred to sulfate-free medium, they released 2-naphthoate and [5,6,7,8]-tetrahydro-2-naphthoate while still consuming naphthalene. With 2-naphthoate as initial substrate, cells produced [5,6,7,8]-tetrahydro-2-naphthoate and the hydrocarbon, naphthalene, indicating reversibility of the initial naphthalene-metabolizing reaction. The reactions in the absence of sulfate were not coupled to observable growth. Excretion of naphthalenederived metabolites was also achieved in sulfate-rich medium upon addition of the protonophore carbonyl cyanide4-(trifluoromethoxy)phenylhydrazone or the ATPase inhibitor N,N 0-dicyclohexylcarbodiimide. In conclusion, obstruction of electron flow and energy gain by sulfate limitation offers an explanation for the occurrence of naphthalene-derived metabolites in oil reservoirs, and provides a simple experimental tool for gaining insights into the anaerobic naphthalene oxidation pathway from an energetic perspective.

show abstract

Conversion of cis‐2‐carboxycyclohexylacetyl‐CoA in the downstream pathway of anaerobic naphthalene degradation

Cited by 17 publications

References 57 publications

Anaerobic degradation of phenanthrene by a sulfate‐reducing enrichment culture

Anaerobic degradation of phenanthrene by a sulfate‐reducing enrichment culture

The 5,6,7,8-Tetrahydro-2-Naphthoyl-Coenzyme A Reductase Reaction in the Anaerobic Degradation of Naphthalene and Identification of Downstream Metabolites

Effect of energy deprivation on metabolite release by anaerobic marine naphthalene‐degrading sulfate‐reducing bacteria

Contact Info

Product

Resources

About