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

# Malonyl-CoA

Malonyl-CoA is both the building block of fat synthesis and the signal that stops fat being burned at the same time.

Updated 2026-11-01

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## Key facts

- Made by acetyl-CoA carboxylase from acetyl-CoA, bicarbonate and ATP (biotin).
- Donates 2 carbons to each fatty acid synthase turn; the third carbon leaves as CO₂.
- Inhibits CPT-I: it closes the gate for fatty acids into the mitochondrion.
- Rises with insulin (feeding) and falls with glucagon, adrenaline and AMPK (fasting, exercise).

**Also called**
Malonyl coenzyme A

**Formula**
C₂₄H₃₈N₇O₁₉P₃S

**PubChem**
[CID 644066](https://pubchem.ncbi.nlm.nih.gov/compound/644066)

## Structure

- A malonyl group (3 C, with a free carboxyl) linked by a thioester to coenzyme A.

## Clinical notes

- Its decarboxylase (MLYCD) is missing in malonic aciduria, with hypoglycaemia and cardiomyopathy.
- In the hypothalamus malonyl-CoA takes part in the satiety signal.

## Pathways

- [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/)

## Related conditions

- [Obesity](https://durgical.com/en/conditions/obesity/)
- [Metabolic syndrome](https://durgical.com/en/conditions/metabolic-syndrome/)

## Related

- [Acetyl-CoA carboxylase (ACC)](https://durgical.com/en/biochemistry/enzymes/acetyl-coa-carboxylase/)
- [Fatty acid synthase (FAS)](https://durgical.com/en/biochemistry/enzymes/fatty-acid-synthase/)
- [Carnitine palmitoyltransferase I (CPT-I)](https://durgical.com/en/biochemistry/enzymes/carnitine-palmitoyltransferase-i/)
- [Acetyl-CoA](https://durgical.com/en/biochemistry/molecules/acetyl-coa/)
- [Carnitine shuttle](https://durgical.com/en/biochemistry/topics/carnitine-shuttle/)

## Test yourself

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

## Which enzyme makes malonyl-CoA?

Acetyl-CoA carboxylase, with biotin and ATP.

## Which β-oxidation enzyme does malonyl-CoA inhibit?

Carnitine palmitoyltransferase I (CPT-I).

## What happens to the carboxyl that ACC adds to malonyl-CoA?

It leaves as CO₂ at condensation; that release makes the step irreversible.

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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: [Malonyl CoA (CID 644066)](https://pubchem.ncbi.nlm.nih.gov/compound/644066) (PubChem, NCBI, 2026) · Public domain; [Fatty acyl-CoA biosynthesis](https://reactome.org/PathwayBrowser/#/R-HSA-75105) (Reactome, 2026); [Carnitine shuttle](https://reactome.org/PathwayBrowser/#/R-HSA-200425) (Reactome, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/molecules/malonyl-coa/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/molecules/malonyl-coa/