TY  - JOUR
A1  - Katsyv, Alexander
A1  - Jain, Surbhi
A1  - Basen, Mirko
A1  - Müller, Volker
T1  - Electron carriers involved in autotrophic and heterotrophic acetogenesis in the thermophilic bacterium Thermoanaerobacter kivui
T2  - Extremophiles
N2  - Thermoanaerobacter kivui is an acetogenic model organism that reduces CO2 with electrons derived from H2 or CO, or from organic substrates in the Wood–Ljugdahl pathway (WLP). For the calculation of ATP yields, it is necessary to know the electron carriers involved in coupling of the oxidative and reductive parts of metabolism. Analyses of key catabolic oxidoreductases in cell-free extract (CFE) or with purified enzymes revealed the physiological electron carriers involved. The glyceraldehyde-3-phosphate dehydrogenase (GA3P-DH) assayed in CFE was NAD+-specific, NADP+ was used with less than 4% and ferredoxin (Fd) was not used. The methylene-THF dehydrogenase was NADP+-specific, NAD+ or Fd were not used. A Nfn-type transhydrogenase that catalyzes reduced Fd-dependent reduction of NADP+ with NADH as electron donor was also identified in CFE. The electron carriers used by the potential electron-bifurcating hydrogenase (HydABC) could not be unambiguously determined in CFE for technical reasons. Therefore, the enzyme was produced homologously in T. kivui and purified by affinity chromatography. HydABC contained 33.9 ± 4.5 mol Fe/mol of protein and FMN; it reduced NADP+ but not NAD+. The methylene-THF reductase (MetFV) was also produced homologously in T. kivui and purified by affinity chromatography. MetFV contained 7.2 ± 0.4 mol Fe/mol of protein and FMN; the complex did neither use NADPH nor NADH as reductant but only reduced Fd. In sum, these analysis allowed us to propose a scheme for entire electron flow and bioenergetics in T. kivui.
KW  - Acetogenic metabolism
KW  - Extremophile
KW  - Electron-bifurcating hydrogenase
KW  - Methylene-THF reductase
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/69567
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-695675
SN  - 1433-4909
N1  - We are grateful to the Deutsche Forschungsgemeinschaft (DFG) and the Bundesministerium für Bildung und Forschung (BMBF; ThermoSynCon) for financial support.
N1  - Open Access funding enabled and organized by Projekt DEAL.
VL  - 25
IS  - 5-6
SP  - 513
EP  - 526
PB  - Springer
CY  - Tokyo
ER  -