Mechanistic studies of the coenzyme F420-reducing formate dehydrogenase from Methanobacterium formicicum

Schauer, Neil L.; Ferry, James G.; Honek, John F.; Orme‐Johnson, William H.; Walsh, Christopher T.

doi:10.1021/bi00370a059

Cited by 29 publications

(22 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1), which provide electrons to the last reductive step of methanogenesis and potentially the first step via electron bifurcation (1,6,7), can be substituted by formate dehydrogenase (Fdh) during growth on formate (7). The F 420 -reducing hydrogenases (Fru and Frc) generate F 420 H 2 for the second and third reductive steps of methanogenesis, but the Fdh is also F 420 reducing (12,13). The hydrogenase Hmd catalyzes the second reductive step directly with H 2 , but its function is redundant with Mtd, which uses reduced F 420 for the same purpose (11).…”

Section: Resultsmentioning

confidence: 99%

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

Lie

Costa

Lupa

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

108

114

View full text Add to dashboard Cite

Despite decades of study, electron flow and energy conservation in methanogenic Archaea are still not thoroughly understood. For methanogens without cytochromes, flavin-based electron bifurcation has been proposed as an essential energy-conserving mechanism that couples exergonic and endergonic reactions of methanogenesis. However, an alternative hypothesis posits that the energy-converting hydrogenase Eha provides a chemiosmosis-driven electron input to the endergonic reaction. In vivo evidence for both hypotheses is incomplete. By genetically eliminating all nonessential pathways of H 2 metabolism in the model methanogen Methanococcus maripaludis and using formate as an additional electron donor, we isolate electron flow for methanogenesis from flux through Eha. We find that Eha does not function stoichiometrically for methanogenesis, implying that electron bifurcation must operate in vivo. We show that Eha is nevertheless essential, and a substoichiometric requirement for H 2 suggests that its role is anaplerotic. Indeed, H 2 via Eha stimulates methanogenesis from formate when intermediates are not otherwise replenished. These results fit the model for electron bifurcation, which renders the methanogenic pathway cyclic, and as such requires the replenishment of intermediates. Defining a role for Eha and verifying electron bifurcation provide a complete model of methanogenesis where all necessary electron inputs are accounted for. M ethanogenesis is an anaerobic respiration carried out by a phylogenetically related group of Archaea within the phylum Euryarchaeota. Methanogens are divided into two metabolic types, those without and those with cytochromes (1). Methanogens without cytochromes use H 2 as an electron donor and are termed hydrogenotrophic. Some species can substitute H 2 with formate, and a few can use secondary alcohols. CO 2 is the electron acceptor and is reduced to methane. Methanogens with cytochromes reduce certain methyl compounds or the methyl carbon of acetate to methane and are called methylotrophic. Many can also use H 2 and CO 2 , as can hydrogenotrophic methanogens.Although the pathways of methanogenesis have long been known, an understanding of energy conservation has been slower to emerge. Methanogens with and without cytochromes both export Na + when a methyl group is transferred from the carrier tetrahydromethanopterin (H 4 MPT) to coenzyme M (CoM) (Fig. 1). The Na + gradient across the membrane is used directly for ATP synthesis or is converted by an antiporter to a proton gradient. However, for methanogenesis from CO 2 , the initial reduction of CO 2 to a formyl group attached to methanofuran (MFR) is endergonic. How energy is provided to drive this reaction is not well understood. Methanogens with and without cytochromes have membrane-associated energy-converting hydrogenases that couple the reduction of low-potential ferredoxins (Fd) to a chemiosmotic membrane gradient (2). If such a Fd donates electrons for CO 2 reduction, an energy-converting hydrogenase is the conduit of ener...

show abstract

Section: Resultsmentioning

confidence: 99%

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

Lie

Costa

Lupa

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

108

114

View full text Add to dashboard Cite

show abstract

“…9). Like most other F 420 -dependent enzymes (255), hydride transfer to C-5 of F 420 is Si-face stereospecific (254).…”

Section: Ffd: F 420 -Reducing Formate Dehydrogenasementioning

confidence: 92%

“…The large subunit is homologous with the structurally characterized bacterial formate dehydrogenases (247), and it is predicted to contain a molybdopterin guanine nucleotide cofactor (MGD) (248-252) and a [4Fe4S] center (190). The small subunit is unique to methanogenic archaea and is predicted to contain two [4Fe4S] clusters (190), an FAD cofactor (190,253,254), and an F 420 -binding site that is homologous to FrhB (150). It has been proposed that formate is oxidized at the molybdopterin center and that electrons are shuttled via the FeS clusters to the electron gate FAD and finally to F 420 (254) (Fig.…”

Section: Ffd: F 420 -Reducing Formate Dehydrogenasementioning

confidence: 99%

“…The small subunit is unique to methanogenic archaea and is predicted to contain two [4Fe4S] clusters (190), an FAD cofactor (190,253,254), and an F 420 -binding site that is homologous to FrhB (150). It has been proposed that formate is oxidized at the molybdopterin center and that electrons are shuttled via the FeS clusters to the electron gate FAD and finally to F 420 (254) (Fig. 9).…”

Section: Ffd: F 420 -Reducing Formate Dehydrogenasementioning

confidence: 99%

See 1 more Smart Citation

Physiology, Biochemistry, and Applications of F₄₂₀- and F_o-Dependent Redox Reactions

Greening

Ahmed

Mohamed

et al. 2016

Microbiol Mol Biol Rev

159

208

View full text Add to dashboard Cite

SUMMARY5-Deazaflavin cofactors enhance the metabolic flexibility of microorganisms by catalyzing a wide range of challenging enzymatic redox reactions. While structurally similar to riboflavin, 5-deazaflavins have distinctive and biologically useful electrochemical and photochemical properties as a result of the substitution of N-5 of the isoalloxazine ring for a carbon. 8-Hydroxy-5-deazaflavin (Fo) appears to be used for a single function: as a light-harvesting chromophore for DNA photolyases across the three domains of life. In contrast, its oligoglutamyl derivative F420is a taxonomically restricted but functionally versatile cofactor that facilitates many low-potential two-electron redox reactions. It serves as an essential catabolic cofactor in methanogenic, sulfate-reducing, and likely methanotrophic archaea. It also transforms a wide range of exogenous substrates and endogenous metabolites in aerobic actinobacteria, for example mycobacteria and streptomycetes. In this review, we discuss the physiological roles of F420in microorganisms and the biochemistry of the various oxidoreductases that mediate these roles. Particular focus is placed on the central roles of F420in methanogenic archaea in processes such as substrate oxidation, C1pathways, respiration, and oxygen detoxification. We also describe how two F420-dependent oxidoreductase superfamilies mediate many environmentally and medically important reactions in bacteria, including biosynthesis of tetracycline and pyrrolobenzodiazepine antibiotics by streptomycetes, activation of the prodrugs pretomanid and delamanid byMycobacterium tuberculosis, and degradation of environmental contaminants such as picrate, aflatoxin, and malachite green. The biosynthesis pathways of Foand F420are also detailed. We conclude by considering opportunities to exploit deazaflavin-dependent processes in tuberculosis treatment, methane mitigation, bioremediation, and industrial biocatalysis.

show abstract

“…Indirect evidence is available indicating that the enzyme could contain dithiothreitol; SDS-PAGE, SDS-polyacrylamide gel electrophoresis; FPLC, fast protein liquid chromatography; CHO-MFR, formylmethanofuran; MFR, methanofuran molybdenum: (i) formylmethanofuran dehydrogenase is rapidly inactivated by cyanide [1], which is a property of many molybdoproteins [5]; (ii) the dehydrogenase catalyzes a reaction analogous to that mediated by xanthine dehydrogenases [6] and formate dehydrogenases [7][8][9], which are molybdoproteins [9]; and (iii) growth of methanogenic bacteria is dependent on molybdenum [10,11], the amounts required being relatively high indicating a catabolic function.…”

Section: Cho-mfr + 2 MV + H20 ~ Co2 + Mfr + 2 Mv-+ 2 H +mentioning

confidence: 99%

Formylmethanofuran dehydrogenase from methanogenic bacteria, a molybdoenzyme

et al. 1989

View full text Add to dashboard Cite

Formylmethanofuran dehydrogenase, a key enzyme of methanogenesis, was purified 100-fold from methanol grown Methanosarcina barkeri to apparent homogeneity and a specific activity of 34/zmol.min -1.rag protein-L Molybdenum was found to co-migrate with the enzyme activity. The molybdenum content of purified preparations was 3-4 nmol per mg protein equal to 0.64).8 mol molybdenum per tool enzyme of apparent molecular mass 200 kDa. Evidence is presented that also formylmethanofuran dehydrogenase from Hz/CO 2 grown Methanobacterium thermoautotrophicum (strain Marburg) is a molybdoenzyme.

show abstract

Mechanistic studies of the coenzyme F420-reducing formate dehydrogenase from Methanobacterium formicicum

Cited by 29 publications

References 22 publications

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

Physiology, Biochemistry, and Applications of F₄₂₀- and F_o-Dependent Redox Reactions

Formylmethanofuran dehydrogenase from methanogenic bacteria, a molybdoenzyme

Contact Info

Product

Resources

About

Mechanistic studies of the coenzyme F420-reducing formate dehydrogenase from Methanobacterium formicicum

Cited by 29 publications

References 22 publications

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

Essential anaplerotic role for the energy-converting hydrogenase Eha in hydrogenotrophic methanogenesis

Physiology, Biochemistry, and Applications of F420- and Fo-Dependent Redox Reactions

Formylmethanofuran dehydrogenase from methanogenic bacteria, a molybdoenzyme

Contact Info

Product

Resources

About

Physiology, Biochemistry, and Applications of F₄₂₀- and F_o-Dependent Redox Reactions