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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),
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