Carboxylation Reactions of Pyruvate: Ferredoxin Oxidoreductase and 2-Oxoglutarate: Ferredoxin Oxidoreductase from Hydrogenobacter thermophilus TK-6

Enzymatic reactions involving pyruvate: ferredoxin oxidoreductase and 2-oxoglutarate: ferredoxin oxidoreductase from a thermophilic, aerobic, chemolithoautotrophic, and hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, were investigated as the CO₂ exchange reaction and CO₂ fixation reaction using ferredoxin isolated from the same organism as a reductant. The reduced ferredoxin was required in the pyruvate synthetic reaction and the 2-oxoglutarate synthetic reaction by a cell extract that had been treated with a PD-10 column to remove the low molecular weight substances. [¹⁴C]Pyruvate and [¹⁴C]2-oxoglutarate were detected as products of pyruvate synthetic and 2-oxoglutarate synthetic reactions, respectively. Further evidence for the operation of pyruvate: ferredoxin oxidoreductase and 2-oxoglutarate: ferredoxin oxidoreductase was obtained from experiments on CO₂ exchange reactions using the purified enzymes.