Biochemistry · Molecule
Acetyl-CoA !
Acetyl-CoA is where sugars, fats and proteins meet: it enters the Krebs cycle or is used to make fat, cholesterol and ketone bodies.
Updated 2026-10-31
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Key facts
- An acetyl group (2 C) joined by a high-energy thioester to coenzyme A, which comes from pantothenic acid (B5).
- Sources: pyruvate (PDH), fatty acid β-oxidation and some amino acids (ketogenic).
- Acetyl-CoA cannot be turned into glucose: PDH is irreversible.
- It activates pyruvate carboxylase and slows PDH.
- Also called
- Acetyl coenzyme A
- Formula
- C₂₃H₃₈N₇O₁₇P₃S
- PubChem
- CID 444493
Structure
- The working part is the thioester at the cysteamine end; the rest (pantetheine, ADP) is a handle for the enzymes.
Clinical notes
- With little insulin and lots of fat released, the liver turns extra acetyl-CoA into ketone bodies: diabetic ketoacidosis.
- Acetyl-CoA is the building block of cholesterol (the HMG-CoA reductase pathway, the target of statins).
Pathways
- Krebs cycle (citric acid cycle)
- Cholesterol synthesis (mevalonate pathway)
- Fatty acid synthesis (lipogenesis)
- Fatty acid β-oxidation
- Ketogenesis (ketone body synthesis)
- Branched-chain amino acid breakdown (leucine route)
- Serotonin and melatonin synthesis
- Ethanol metabolism
Related conditions
Related
Test yourself
Think of the answer, then tap the question to see it.
Why can't fatty acids give net glucose in humans?
They yield acetyl-CoA, and PDH is irreversible: the two carbons are lost as CO₂ in the cycle.
Which vitamin is coenzyme A made from?
Pantothenic acid (B5).
What does the liver do with excess acetyl-CoA in prolonged fasting?
It makes ketone bodies (acetoacetate and β-hydroxybutyrate).
Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Acetyl coenzyme A (CID 444493) (PubChem, NCBI, 2026) · Public domain; Pyruvate metabolism (Reactome, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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