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

# Cyclic AMP (cAMP)

The classic second messenger: adenylyl cyclase makes it from ATP when a hormone arrives, and phosphodiesterase destroys it.

Updated 2026-11-01

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## Key facts

- Adenylyl cyclase makes it (ATP → cAMP + pyrophosphate) and phosphodiesterases break it down (cAMP → AMP).
- It activates PKA, the Epac protein and some ion channels (vision and smell, for example, use cyclic nucleotides).
- Second messenger of glucagon, adrenaline (β), ACTH, TSH, LH, FSH, PTH, ADH (V2), hCG, CRH, GHRH and calcitonin.
- Insulin lowers it by activating phosphodiesterase 3B: that is how it stops lipolysis and glycogen breakdown.

**Also called**
Adenosine 3',5'-cyclic monophosphate, cAMP

**Formula**
C10H12N5O6P

**PubChem**
[CID 6076](https://pubchem.ncbi.nlm.nih.gov/compound/6076)

## Structure

- Adenine linked to ribose, with a single phosphate forming a ring between the ribose 3' and 5' carbons.
- That cyclic phosphodiester bond is what phosphodiesterase breaks to give 5'-AMP.

## Clinical notes

- Caffeine and theophylline inhibit phosphodiesterases and prolong cAMP (bronchodilation, cardiac stimulation).
- Phosphodiesterase 3 inhibitors (milrinone) are used in acute heart failure; phosphodiesterase 4 inhibitors in inflammatory skin and lung disease.
- Cholera diarrhoea is due to high cAMP in the enterocyte.

## Related conditions

- [Asthma](https://durgical.com/en/conditions/asthma/)

## Related

- [Adenylyl cyclase](https://durgical.com/en/biochemistry/enzymes/adenylyl-cyclase/)
- [Protein kinase A (PKA)](https://durgical.com/en/biochemistry/enzymes/protein-kinase-a/)
- [G protein-coupled receptors and cAMP](https://durgical.com/en/biochemistry/topics/g-protein-coupled-receptors-and-camp/)
- [Glucagon signalling](https://durgical.com/en/biochemistry/topics/glucagon-signalling/)
- [ATP (adenosine triphosphate)](https://durgical.com/en/biochemistry/molecules/atp/)
- [Insulin signalling](https://durgical.com/en/biochemistry/topics/insulin-signalling/)

## Test yourself

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

## Which enzyme makes cAMP and which breaks it down?

Adenylyl cyclase makes it from ATP and phosphodiesterase breaks it down to 5'-AMP.

## How does insulin lower adipocyte cAMP?

Through Akt it activates phosphodiesterase 3B, which breaks down cAMP and switches off hormone-sensitive lipase.

## Why does theophylline raise cAMP?

Because it inhibits the phosphodiesterases that break it down.

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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: [Camp (CID 6076)](https://pubchem.ncbi.nlm.nih.gov/compound/6076) (PubChem, NCBI, 2026) · Public domain; [PRKACA: cAMP-dependent protein kinase catalytic subunit alpha (human)](https://www.uniprot.org/uniprotkb/P17612/entry) (UniProt, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

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