A reversible electron-bifurcating ferredoxin- and NAD-dependent [FeFe]-hydrogenase (HydABC) in Moorella thermoacetica.
J Bacteriol
; 195(6): 1267-75, 2013 Mar.
Article
en En
| MEDLINE
| ID: mdl-23316038
Moorella 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 µmol 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 µmol min(-1) mg protein(-1) in the stoichiometry Fd(ox) + NAD(+) + 2H(2) 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.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Moorella
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Ferredoxinas
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Flavoproteínas
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Hidrógeno
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Hidrogenasas
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Proteínas Hierro-Azufre
Idioma:
En
Revista:
J Bacteriol
Año:
2013
Tipo del documento:
Article
País de afiliación:
Alemania
Pais de publicación:
Estados Unidos