AcetoacetateCoA

Acetoacetyl-CoA is a crucial intermediate molecule in metabolism. It is a thioester formed from acetoacetate and coenzyme A. This molecule plays a central role in both the synthesis and breakdown of fatty acids.

In fatty acid synthesis, acetoacetyl-CoA is the first four-carbon product generated by the enzyme acetyl-CoA carboxylase. It is then reduced by NADPH to form beta-hydroxybutyryl-CoA and subsequently elongated to longer chain fatty acids. This pathway occurs primarily in the cytoplasm of liver cells and adipocytes.

In the breakdown of fatty acids, also known as beta-oxidation, acetoacetyl-CoA is produced from the cleavage of a six-carbon fatty acid. It can then be cleaved into two molecules of acetyl-CoA, which can enter the citric acid cycle for energy production. Alternatively, acetoacetyl-CoA can be converted into ketone bodies in the liver, which serve as an alternative fuel source for tissues like the brain during prolonged fasting or starvation. The interconversion between acetoacetyl-CoA and other metabolic intermediates highlights its importance in energy homeostasis and nutrient utilization.