Butyryl-CoA (or butyryl-coenzyme A, butanoyl-CoA) is an Organic compound coenzyme A-containing derivative of butyric acid.
From redox data, butyryl-CoA dehydrogenase shows little to no activity at pH higher than 7.0. This is important as enzyme midpoint potential is at pH 7.0 and at 25 °C. Therefore, changes above from this value will denature the enzyme.
Within the human colon, butyrate helps supply energy to the gut epithelium and helps regulate cell responses.
Butyryl-CoA has a very high calculated potential Gibbs energy, -462.53937 kcal/mol, stored at its bond with CoA.
Reaction
Fatty acid metabolism
Butyryl-CoA interconverts to and from 3-oxohexanoyl-CoA by acetyl-CoA acetyltransferase (or
thiolase).
In terms of organic chemistry, the reaction is the reverse of a Claisen condensation.
Subsequently butyryl-CoA is converted into crotonyl-CoA. The conversion is catalyzed by electron-transfer flavoprotein 2,3-oxidoreductase.
This enzyme has many synonyms that are orthologous to each other, including butyryl-CoA dehydrogenase,
acyl-CoA dehydrogenase,
acyl-CoA oxidase,
and short-chain 2-methylacyl-CoA dehydrogenase
Fermentation
Butyryl-CoA is an intermediate of the fermentation pathway found in
Clostridium kluyveri.
This species can ferment acetyl-CoA and
succinate into
butanoate, extracting energy through the process.
The fermentation pathway from ethanol to acetyl-CoA to butanoate is also known as ABE fermentation.
Butyryl-CoA is reduced from
crotonyl-CoAcatalyzing by butyryl-CoA dehydrogenase, where two
NADH molecules donate four electrons, with two of them reducing
ferredoxin (2Fe-2S cluster) and the other two reducing crotonyl-CoA into butyryl-CoA.
Subsequently, butyryl-CoA is converted into butanoate by propionyl-CoA transferase, which transfers the coenzyme-A group onto an
acetate, forming
acetyl-CoA.
It is essential in reducing ferredoxins in anaerobic bacteria and archaea so that electron transport phosphorylation and substrate-level phosphorylation can occur with increased efficiency.
4-Aminobutanoate (GABA) degradation
Butyryl-CoA is also an intermediate found in 4-aminobutanoate (GABA) degradation.
4-aminobutanoate (GABA) has two fates in this degradation pathway. When discovered in
Acetoanaerobium sticklandii and
Pseudomonas fluorescens, 4-aminobutanoate was converted into
L-glutamate, which can be deaminated, releasing
ammonium.
However, in
Acetoanaerobium sticklandii and
Clostridium aminobutyricum, 4-aminobutanoate was converted into succinate semialdehyde and, through a series of steps via the intermediate of
butanoyl-CoA, finally converted into
butanoate.
The degradation pathway plays an important role in regulating the concentration of GABA, which is an inhibitory neurotransmitter that reduces neuronal excitability.
Regulation
Butyryl-CoA acts upon butanol dehydrogenase via competitive inhibition. The adenine moiety can bind butanol dehydrogenase and reduce its activity.
The phosphate moiety of butyryl-CoA is found to have inhibitory activities upon its binding with phosphotransbutyrylase.
Butyryl-CoA is also believed to have inhibitory effects on acetyl-CoA acetyltransferase,
See also
Further reading
