The synthesis of acetyl-CoA by Clostridium thermoaceticum from carbon dioxide, hydrogen, coenzyme A and methyltetrahydrofolate

Abstract

It has been demonstrated that enzymes from Clostridium thermoaceticum catalyze the following reaction in which Fd is ferredoxin and CH₃THF is methyltetrahydrofolate. $$\begin{gathered}{\text{CO}}_{\text{2}} {\text{ + H}}_{\text{2}} {\text{ + CH}}_{\text{3}} {\text{THF + }} {\text{CoASH}}\xrightarrow{{{\text{ATP, Fd}}}} \hfill \\{\text{CH}}_{\text{3}} {\text{COSCoA + THF + H}}_{\text{2}} {\text{O}}{\text{.}} \hfill \\\end{gathered}$$ The system involves hydrogenase, CO dehydrogenase, a methyltransferase, a corrinoid enzyme and other unknown components. Hydrogenase catalyzes the reduction of ferredoxin by H₂; CO dehydrogenase then uses the reduced ferredoxin to reduce CO₂ to a one-carbon intermediate that combined with CoASH and with a methyl group originating from CH₃THF to form acetyl-CoA. It is proposed that these reactions are part of the mechanism which enables certain acetogenic autotrophic bacteria to grow on CO₂ and H₂.