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[Biochemistry](https://durgical.com/en/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](https://pubchem.ncbi.nlm.nih.gov/compound/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)](https://durgical.com/en/biochemistry/pathways/krebs-cycle/)
- [Cholesterol synthesis (mevalonate pathway)](https://durgical.com/en/biochemistry/pathways/cholesterol-synthesis/)
- [Fatty acid synthesis (lipogenesis)](https://durgical.com/en/biochemistry/pathways/fatty-acid-synthesis/)
- [Fatty acid β-oxidation](https://durgical.com/en/biochemistry/pathways/fatty-acid-oxidation/)
- [Ketogenesis (ketone body synthesis)](https://durgical.com/en/biochemistry/pathways/ketogenesis/)
- [Branched-chain amino acid breakdown (leucine route)](https://durgical.com/en/biochemistry/pathways/branched-chain-amino-acid-breakdown/)
- [Serotonin and melatonin synthesis](https://durgical.com/en/biochemistry/pathways/serotonin-and-melatonin-synthesis/)
- [Ethanol metabolism](https://durgical.com/en/biochemistry/pathways/ethanol-metabolism/)

## Related conditions

- [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/)
- [Pyruvate dehydrogenase deficiency](https://durgical.com/en/conditions/pyruvate-dehydrogenase-deficiency/)

## Related

- [Pyruvate dehydrogenase complex (PDH)](https://durgical.com/en/biochemistry/enzymes/pyruvate-dehydrogenase-complex/)
- [Citrate synthase](https://durgical.com/en/biochemistry/enzymes/citrate-synthase/)
- [Pyruvate](https://durgical.com/en/biochemistry/molecules/pyruvate/)
- [Citrate](https://durgical.com/en/biochemistry/molecules/citrate/)

## 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).

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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)](https://pubchem.ncbi.nlm.nih.gov/compound/444493) (PubChem, NCBI, 2026) · Public domain; [Pyruvate metabolism](https://reactome.org/PathwayBrowser/#/R-HSA-70268) (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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Representative model, for educational purposes only.

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