Reductive acetyl-CoA pathway
Encyclopedia
The Wood–Ljungdahl pathway is a set of biochemical reactions used by some bacteria
and archaea
. It is also known as the reductive acetyl–CoA pathway. This pathway enables certain organisms to use hydrogen as an electron donor and carbon dioxide as an electron acceptor as well as a building block for biosynthesis.
In this pathway carbon dioxide
is reduced to carbon monoxide
, which is then converted to acetyl coenzyme A. Two enzymes participate, 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.
The pathway occurs in bacteria and archaea, e.g. methanogen
s and in acetate-producing
bacteria such as Clostridium
. Unlike the Reverse Krebs cycle
and the Calvin cycle
, this process is not cyclic.
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and archaea
Archaea
The Archaea are a group of single-celled microorganisms. A single individual or species from this domain is called an archaeon...
. It is also known as the reductive acetyl–CoA pathway. This pathway enables certain organisms to use hydrogen as an electron donor and carbon dioxide as an electron acceptor as well as a building block for biosynthesis.
In this pathway carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
is reduced to carbon monoxide
Carbon monoxide
Carbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
, which is then converted to acetyl coenzyme A. Two enzymes participate, 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.
The pathway occurs in bacteria and archaea, e.g. methanogen
Methanogen
Methanogens are microorganisms that produce methane as a metabolic byproduct in anoxic conditions. They are classified as archaea, a group quite distinct from bacteria...
s and in acetate-producing
Acetogen
An acetogen is a microorganism that generates acetate as a product of anaerobic respiration. This process is known as acetogenesis and is different from acetate fermentation, although both occur in the absence of oxygen and produce acetate...
bacteria such as Clostridium
Clostridium
Clostridium is a genus of Gram-positive bacteria, belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster or spindle...
. Unlike the Reverse Krebs cycle
Reverse Krebs cycle
The reverse Krebs cycle...
and the Calvin cycle
Calvin cycle
The Calvin cycle or Calvin–Benson-Bassham cycle or reductive pentose phosphate cycle or C3 cycle or CBB cycle is a series of biochemical redox reactions that take place in the stroma of chloroplasts in photosynthetic organisms...
, this process is not cyclic.