Ketolysis

Ketolysis is the degradation (the breaking down) of ketone bodies into simpler molecules to be employed as fuel in the production of ATP by the cell mitochondria. This metabolic pathway only takes place in the absence of glucose, during starvation or when the individual is on a ketogenic diet.

Metabolic process

The ketone body Beta-hydroxybutyrate is produced by the liver cell mitochondria from fatty acid, which in turn derives from the saturated fat we eat or from the adipose tissue we have as a store of energy in our body. Once this ketone body is released, it travels in the bloodstream and gets into our brain through the brain blood barrier. There, it gets into the nerve cell cytoplasms where it is degraded first into acetoacetate, through the intervention of ß-hydroxybutyrate Dehydrogenase enzyme, and then into acetoacetyl CoA thanks to the CoA Transferase (Thiophorase) enzyme. The CoA (coenzyme A) is added to acetoacetyl by the molecule succinyl CoA, which is an intermediate of the TCA cycle.

Finally, acetoacetyl CoA gets split into two molecules of acetyl CoA; this is done by the Thyolase enzyme. Each of the acetyl CoA can be used in the TCA cycle for the production of ATP (Adenine TriphosPhate), yielding 10 ATPs each.

Below, a complete diagram of ketolysis