还原性乙酰辅酶A途径(Reductive acetyl CoA pathway)

Unlike rTCA and RuBP, rACA is a noncyclic pathway. One CO₂ is captured on a special cofactor (tetrahydrofolate: T in the figure) and reduced to a methyl group. The other CO₂ is reduced to a carobonyl group (C=O) by carbon monoxide dehydrogenase and this enzyme bound carbonyl group is combined with the methyl group to form acetyl CoA by a collection of enzymes termed the acetyl CoA synthase complex. The pathway seems to require hydrogen gas as the electron donor and it is very efficient, requiring only 4H₂ per acetate formed.

Some of its practitioners include, acetogens (microbes that generate acetic acid from hydrogen -0 Clostridium thermoaceticum, Acetobacterium woodii), methanogens (Methanobacterium thermoautotrophicum) and most autotrophic sulfate reducers (Defulfobacterium autotrophicum).

Figure 1 - Reaction of the reductive acetyl CoA pathway. Note that the above is a general diagram and the exact reactions in any species can vary. T: tetrahydrofolate, Co: A corrinoid protein (another type of methyl group carrier),