CO2‐reduction to formate by NADPH. The initial step in the total synthesis of acetate from CO2 in Clostridium thermoaceticum

Thauer, Rudolf K.

doi:10.1016/0014-5793(72)80421-6

Cited by 79 publications

(41 citation statements)

References 15 publications

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“…The NADH and the reduced ferredoxin required for H 2 formation via HydABC are regenerated during glucose oxidation to 2 acetic acid and 2 CO 2 in the NAD-specific glyceraldehyde phosphate dehydrogenase reaction (10,43) and the pyruvate:ferredoxin oxidoreductase reaction (32,44). Since most of the NADH and reduced ferredoxin are reoxidized during the reduction of 2 CO 2 to acetic acid (10), the HydABC complex probably has the function of a valve that allows glucose oxidation and thus ADP phosphorylation when CO 2 reduction to acetic acid becomes rate limiting.…”

Section: Discussionmentioning

confidence: 99%

A Reversible Electron-Bifurcating Ferredoxin- and NAD-Dependent [FeFe]-Hydrogenase (HydABC) in Moorella thermoacetica

Wang

Huang

Kahnt

et al. 2013

Journal of Bacteriology

118

144

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bMoorella thermoacetica was long the only model organism used to study the biochemistry of acetogenesis from CO 2 . Depending on the growth substrate, this Gram-positive bacterium can either form H 2 or consume it. Despite the importance of H 2 in its metabolism, a hydrogenase from the organism has not yet been characterized. We report here the purification and properties of an electron-bifurcating [FeFe]-hydrogenase from M. thermoacetica and show that the cytoplasmic enzyme efficiently catalyzes both H 2 formation and H 2 uptake. The purified heterotrimeric iron-sulfur flavoprotein (HydABC) catalyzed the coupled reduction of ferredoxin (Fd) and NAD ؉ with H 2 at 55°C at pH 7.5 at a specific rate of about 100 mol min ؊1 mg protein ؊1 and the reverse reaction, the coupled reduction of protons to H 2 with reduced ferredoxin and NADH, at a specific rate of about 10 mol min ؊1 mg protein ؊1 in the stoichiometry Fd ox ؉ NAD ؉ ؉ 2H 2 ª Fd red 2؊ ؉ NADH ؉ 3H ؉ . When ferredoxin from Clostridium pasteurianum, NAD ؉ , and the enzyme were incubated at pH 7.0 under 100% H 2 in the gas phase (E 0 = ‫؍‬ ؊414 mV), more than 95% of the ferredoxin (E 0 = ‫؍‬ ؊400 mV) was reduced, which indicated that ferredoxin reduction with H 2 is driven by the exergonic reduction of NAD ؉ (E 0 = ‫؍‬ ؊320 mV) with H 2 . In the absence of NAD ؉ , ferredoxin was not reduced. We identified the genes encoding HydABC within the transcriptional unit hydCBAX and mapped the transcription start site.

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Section: Discussionmentioning

confidence: 99%

A Reversible Electron-Bifurcating Ferredoxin- and NAD-Dependent [FeFe]-Hydrogenase (HydABC) in Moorella thermoacetica

Wang

Huang

Kahnt

et al. 2013

Journal of Bacteriology

118

144

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“…The most common class catalyze the direct transfer of a hydride moiety from formate to NAD(P) ϩ , but it is difficult to drive them in reverse because the reduction potential of NAD(P) ϩ is more positive than that of CO 2 (9). In some prokaryotes, however, the formate dehydrogenases are complex enzymes that contain molybdenum or tungsten cofactors to transfer the electrons from formate oxidation to an independent active site, to reduce quinone, protons, or NAD(P) ϩ (10-13).…”

mentioning

confidence: 99%

Reversible interconversion of carbon dioxide and formate by an electroactive enzyme

Reda

Plugge

Abram

et al. 2008

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

487

420

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Carbon dioxide (CO2) is a kinetically and thermodynamically stable molecule. It is easily formed by the oxidation of organic molecules, during combustion or respiration, but is difficult to reduce. The production of reduced carbon compounds from CO 2 is an attractive proposition, because carbon-neutral energy sources could be used to generate fuel resources and sequester CO 2 from the atmosphere. However, available methods for the electrochemical reduction of CO2 require excessive overpotentials (are energetically wasteful) and produce mixtures of products. Here, we show that a tungsten-containing formate dehydrogenase enzyme (FDH1) adsorbed to an electrode surface catalyzes the efficient electrochemical reduction of CO 2 to formate. Electrocatalysis by FDH1 is thermodynamically reversible-only small overpotentials are required, and the point of zero net catalytic current defines the reduction potential. It occurs under thoroughly mild conditions, and formate is the only product. Both as a homogeneous catalyst and on the electrode, FDH1 catalyzes CO 2 reduction with a rate more than two orders of magnitude faster than that of any known catalyst for the same reaction. Formate oxidation is more than five times faster than CO 2 reduction. Thermodynamically, formate and hydrogen are oxidized at similar potentials, so formate is a viable energy source in its own right as well as an industrially important feedstock and a stable intermediate in the conversion of CO2 to methanol and methane. FDH1 demonstrates the feasibility of interconverting CO2 and formate electrochemically, and it is a template for the development of robust synthetic catalysts suitable for practical applications.electrocatalysis ͉ formate dehydrogenase ͉ formate oxidation ͉ protein film voltammetry ͉ carbon dioxide reduction C arbon dioxide (CO 2 ) is a kinetically and thermodynamically stable molecule that is difficult to chemically activate. As the unreactive product of the combustion of carbon-containing molecules, such as fossil fuels, and biological respiration, it is accumulating in the atmosphere and is a major cause of concern in climate-change scenarios (1, 2). Consequently, catalysts that are able to sequester CO 2 from the atmosphere rapidly and efficiently, to generate reduced carbon compounds for use as fuels or chemical feedstocks, have long been sought after. Organometallic complexes that insert CO 2 into an M-H bond and the use of supercritical CO 2 to facilitate its hydrogenation are two promising approaches to the development of a homogeneous catalytic process (3-5). Extensive efforts to develop electrode materials for the direct, electrochemical reduction of CO 2 have been made also, but so far, they require the application of extreme potentials (are inefficient energetically) or they are nonspecific and produce mixtures of products (4, 6, 7). An efficient and specific method for reducing CO 2 electrochemically has obvious applications in a future energy economy based on the cyclic reduction and oxidation of simple carbon compound...

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“…16 The production and isolation of the enzyme was performed in parallel with that of the well-characterized FDH from Candida boidinii (FDH_CanBo) for comparison and was performed aerobically. As opposed to other highly oxygen-labile acetogen FDHs, [11][12][13] FDH H _CloCa showed increased stability, retaining activity over a few days. To assay FDH H _CloCa and FDH_CanBo in both reaction directions, the equilibrium was approached from either side by using high excesses of formate or CO 2 (in the form of bicarbonate) with a much lower concentration of the corresponding nicotinamide cofactor (NAD + /NADH).…”

Section: Formate Production Through Biocatalysismentioning

confidence: 80%

“…FDHs from such sources are therefore naturally geared toward the generation of formate from CO 2 . Accordingly, there have been several reports of acetogen FDHs showing a higher than normal preference for the reduction of CO 2 coupled to the oxidation of various cofactors, [11][12][13] but an FDH where this surpasses the ability to catalyze formate oxidation has not previously been reported.…”

Section: Formate Production Through Biocatalysismentioning

confidence: 98%

Formate production through biocatalysis

2013

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CO₂‐reduction to formate by NADPH. The initial step in the total synthesis of acetate from CO₂ in Clostridium thermoaceticum

Cited by 79 publications

References 15 publications

A Reversible Electron-Bifurcating Ferredoxin- and NAD-Dependent [FeFe]-Hydrogenase (HydABC) in Moorella thermoacetica

A Reversible Electron-Bifurcating Ferredoxin- and NAD-Dependent [FeFe]-Hydrogenase (HydABC) in Moorella thermoacetica

Reversible interconversion of carbon dioxide and formate by an electroactive enzyme

Formate production through biocatalysis

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