Ketone body oxidation

Ketone body oxidation occurs in a range of tissues outside of the liver as a means of energy production. The reactions, occurring in mitochondria, are almost a reversal of the ketogenesis pathway:

• 3-hydroxybutyrate dehydrogenase converts 3-hydroxybutyrate to acetoacetate
• 3-oxoacid CoA transferase uses succinyl CoA to convert acetoacetate to acetoacetyl CoA. Succinate is produced which is useful for later steps: via a malate intermediate, it is a precursor for oxaloacetate which combines with acetyl CoA.
• acetoacetyl CoA transferase cleaves acetoacetyl CoA into 2 acetyl CoA molecules
• acetyl CoA is fed into the tricarboxylic acid cycle for the production of energy

The enzymes in the reaction are not physiologially saturated and so they are probably controlled by the concentration of ketone bodies within the blood.