Reductive_acetyl-CoA_pathway
Wood–Ljungdahl pathway
A set of biochemical reactions used by some bacteria
The Wood–Ljungdahl pathway is a set of biochemical reactions used by some bacteria. It is also known as the reductive acetyl-coenzyme A (acetyl-CoA) pathway.[1] This pathway enables these organisms to use hydrogen (H2) as an electron donor, and carbon dioxide (CO2) as an electron acceptor and as a building block for biosynthesis.
In this pathway carbon dioxide is reduced to carbon monoxide (CO) and formic acid (HCOOH) or directly into a formyl group (R−CH=O), the formyl group is reduced to a methyl group (−CH3) and then combined with the carbon monoxide and coenzyme A to produce acetyl-CoA. Two specific enzymes participate on the carbon monoxide side of the pathway: CO dehydrogenase and acetyl-CoA synthase. The former catalyzes the reduction of the CO2 and the latter combines the resulting CO with a methyl group to give acetyl-CoA.[1][2]
Some anaerobic bacteria use the Wood–Ljungdahl pathway in reverse to break down acetate. For example, sulfate-reducing bacteria (SRB) transform acetate completely into CO2 and H2 coupled with the reduction of sulfate to sulfide.[3] When operating in the reverse direction, the acetyl-CoA synthase is sometimes called acetyl-CoA decarbonylase.
Not to be confused with the Wood-Ljungdahl pathway, an evolutionarily related but biochemically distinct pathway named the Wolfe Cycle[4] occurs exclusively in some methanogenic archaea called methanogens.[5] In these anaerobic archaea, the Wolfe Cycle functions as a methanogenesis pathway to reduce CO2 into methane (CH4) with electron donors such as hydrogen (H2) and formate (HCOO–).[6]