During prolonged starvation, the brain adapts to use ketone bodies as fuel. Which enzyme in extrahepatic tissues is required to activate acetoacetate before it can enter the TCA cycle?
- A Succinyl-CoA:3-ketoacid CoA transferase (SCOT) ✓
- B Acetoacetyl-CoA thiolase
- C HMG-CoA synthase
- D Acetyl-CoA carboxylase
Correct answer: A. Succinyl-CoA:3-ketoacid CoA transferase (SCOT)
Explanation
SCOT (thiophorase) transfers CoA from succinyl-CoA to acetoacetate, forming acetoacetyl-CoA, which thiolase then splits into two acetyl-CoA for the TCA cycle. This enzyme is absent in the liver, so liver produces but cannot utilize ketone bodies. HMG-CoA synthase and thiolase are part of ketogenesis in liver.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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