[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Acetoacetate (acetoacetic acid)

[Biochemistry](https://durgical.com/en/biochemistry/) · Molecule

# Acetoacetate (acetoacetic acid)

Acetoacetate is the first ketone body the liver makes; other tissues turn it back into acetyl-CoA.

Updated 2026-11-01

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## Key facts

- Released by HMG-CoA lyase in liver mitochondria.
- It is reduced to β-hydroxybutyrate (BDH1) or loses CO₂ on its own to form acetone.
- In tissues SCOT activates it to acetoacetyl-CoA, which gives 2 acetyl-CoA.
- It is what the nitroprusside strip detects in urine and blood.

**Also called**
3-Oxobutanoic acid

**Formula**
C₄H₆O₃

**PubChem**
[CID 96](https://pubchem.ncbi.nlm.nih.gov/compound/96)

## Structure

- A 4-carbon β-keto acid: keto group at C3 and carboxyl at C1, which is why it decarboxylates easily.

## Clinical notes

- The acetone it forms gives the fruity breath of ketoacidosis.
- The nitroprusside strip can underestimate ketosis when β-hydroxybutyrate predominates.

## Pathways

- [Ketogenesis (ketone body synthesis)](https://durgical.com/en/biochemistry/pathways/ketogenesis/)
- [Phenylalanine and tyrosine metabolism](https://durgical.com/en/biochemistry/pathways/phenylalanine-and-tyrosine-metabolism/)
- [Branched-chain amino acid breakdown (leucine route)](https://durgical.com/en/biochemistry/pathways/branched-chain-amino-acid-breakdown/)

## Related conditions

- [Diabetic ketoacidosis](https://durgical.com/en/conditions/diabetic-ketoacidosis/)
- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)

## Related

- [β-Hydroxybutyrate](https://durgical.com/en/biochemistry/molecules/hydroxybutyrate/)
- [Mitochondrial HMG-CoA synthase (HMGCS2)](https://durgical.com/en/biochemistry/enzymes/mitochondrial-hmg-coa-synthase/)
- [β-Hydroxybutyrate dehydrogenase (BDH1)](https://durgical.com/en/biochemistry/enzymes/hydroxybutyrate-dehydrogenase/)
- [Succinyl-CoA:3-ketoacid CoA transferase (SCOT)](https://durgical.com/en/biochemistry/enzymes/succinyl-coa-3-ketoacid-coa-transferase/)
- [Acetyl-CoA](https://durgical.com/en/biochemistry/molecules/acetyl-coa/)

## Test yourself

Think of the answer, then tap the question to see it.

## Which enzyme produces acetoacetate?

HMG-CoA lyase, which splits HMG-CoA into acetoacetate and acetyl-CoA.

## Where does the acetone on the breath in ketoacidosis come from?

From spontaneous decarboxylation of acetoacetate.

## Which ketone body does the nitroprusside strip detect?

Acetoacetate (and to a lesser degree acetone), not 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: [Acetoacetic Acid (CID 96)](https://pubchem.ncbi.nlm.nih.gov/compound/96) (PubChem, NCBI, 2026) · Public domain; [Synthesis of Ketone Bodies](https://reactome.org/PathwayBrowser/#/R-HSA-77111) (Reactome, 2026); [Ketones urine test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003585.htm) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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