acetoacetylCoAksi

Acetoacetyl-CoA is a four-carbon beta-ketoacyl-CoA compound that plays a crucial role in intermediary metabolism. It is a key intermediate in the synthesis of ketone bodies, which are produced in the liver when carbohydrate availability is low, such as during fasting or prolonged exercise. In this pathway, two molecules of acetyl-CoA are condensed to form acetoacetyl-CoA, catalyzed by the enzyme thiolase. This reaction is the first committed step in ketogenesis.

Beyond ketone body synthesis, acetoacetyl-CoA is also an important intermediate in the breakdown of fatty acids through beta-oxidation. However, in this context, it is typically formed from the oxidation of a saturated fatty acid with an even number of carbon atoms. Acetoacetyl-CoA can then be cleaved back into two molecules of acetyl-CoA.

Furthermore, acetoacetyl-CoA is involved in the biosynthesis of cholesterol and other steroids. It is a precursor to 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA), another critical intermediate in the mevalonate pathway, which leads to the synthesis of isoprenoids, including cholesterol. In plants and bacteria, acetoacetyl-CoA is also a precursor for the synthesis of various secondary metabolites. The interconversion between acetoacetyl-CoA and acetyl-CoA, and its participation in anabolic and catabolic pathways, highlights its central position in cellular energy and biosynthesis.