MMT: ketone bodies Flashcards
What are the three main ketone bodies?
Acetoacetate, acetone, and b-hydroxybutyrate
Describe ketone bodies.
A soluble fuel made by the liver during the fasting state that the brain can use
Describe liver metabolism during prolonged fasting.
b-oxidation is ramped up to produce acetyl CoA that can be used for gluconeogenesis as well as ketone body synthesis
Where does ketone body production occur?
Mitochondria in the liver
What are the major enzymes in synthesis of ketone bodies?
- Thiolase
- HMG CoA synthase (mitochondrial enzyme)
- HMG CoA lyase
What are the major intermediates in synthesis of ketone bodies?
- Acetoacetyl CoA
- HMG CoA
- Acetoacetate
- Acetone
What is the most prevalent ketone body? What is significant about this?
b-hydroxybutyrate; oxidation of it produces an extra NADH, making it energy dense
Where are ketone bodies oxidated?
Muscle and other tissues such as the brain
What are the intermediates of oxidation of ketone bodies?
- B-hydroxybutyrate
- Acetoacetate
- Acetoacetyl CoA
- 2 acetyl CoA
What are the enzymes of oxidation of ketone bodies?
- b-hydroxybutyrate dehydrogenase
- succinyl CoA acetoacetate CoA transferase
- thiolase
Which step of ketone oxidation produces NADH?
First one! B-hydroxybutyrate to acetoacetate
Why does oxidation of ketones not occur in the liver?
To ensure formed ketone bodies are not just immediately oxidized in the liver, there is a lack of the enzyme succinyl CoA acetoacetate CoA transferase
What is the energy yield of ketone bodies?
21.5 ATP
Where is the energy cost in ketone oxidation?
Activation of acetoacetate; it requires consumption of succinyl CoA, reducing formation of one GTP in the TCA cycle
How does insulin regulate ketogenesis?
An absence of insulin increases CPTI which decreases malonyl CoA; this results in upregulation of acetyl CoA production. In excess, acetyl CoA will become ketone bodies
