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# Polyamines (putrescine, spermidine, spermine)

Polyamines are small, strongly positive molecules made from ornithine. Growing cells need them, so blocking their synthesis slows parasites and some tumours.

Updated 2026-11-01

## Key facts

- Ornithine decarboxylase (ODC, needs pyridoxal phosphate) turns ornithine into putrescine: the rate-limiting step.
- Decarboxylated SAM (from SAM decarboxylase) donates aminopropyl groups: putrescine → spermidine → spermine.
- At body pH they carry several positive charges and bind DNA, RNA and phospholipids; they are needed for cell growth and division.
- ODC has one of the shortest half-lives of any enzyme (minutes); antizyme sends it to the proteasome without ubiquitin.
- Eflornithine (difluoromethylornithine, DFMO) inhibits ODC irreversibly (suicide inhibitor).

## In detail

- 1. Ornithine comes from arginine (arginase) and is a crossroads between the urea cycle, proline and polyamines.
- 2. ODC is induced by growth factors, hormones and oncogenes such as MYC; polyamine levels are high in rapidly dividing tissues and tumours.
- 3. Spermidine provides the aminobutyl group for hypusine, a unique modified lysine required by translation factor eIF5A.
- 4. Breakdown: acetylation by SSAT and oxidation by polyamine oxidase recycle spermine and spermidine to putrescine; acetylated forms are excreted in urine.
- 5. Polyamines are also eaten in food and made by gut bacteria.

**Also called**
Ornithine decarboxylase, Eflornithine (DFMO)

## Clinical notes

- Eflornithine treats West African sleeping sickness (Trypanosoma brucei gambiense), usually with nifurtimox; trypanosomal ODC is turned over slowly, so the block lasts.
- As a cream, eflornithine slows unwanted facial hair growth; it is also used to lower relapse in high-risk neuroblastoma.
- Raised urinary polyamines were proposed as tumour markers but are not specific.

## Related conditions

- [Colorectal cancer](https://durgical.com/en/conditions/colorectal-cancer/)

## Related

- [S-adenosylmethionine (SAM)](https://durgical.com/en/biochemistry/molecules/s-adenosylmethionine/)
- [Arginase 1](https://durgical.com/en/biochemistry/enzymes/arginase-1/)
- [Vitamin B6 (pyridoxal phosphate)](https://durgical.com/en/biochemistry/molecules/vitamin-b6/)
- [Urea cycle](https://durgical.com/en/biochemistry/pathways/urea-cycle/)
- [Molecules derived from amino acids](https://durgical.com/en/biochemistry/topics/molecules-derived-from-amino-acids/)
- [Ubiquitin–proteasome system](https://durgical.com/en/biochemistry/topics/ubiquitin-proteasome-system/)

## Test yourself

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

## Which enzyme catalyses the rate-limiting step of polyamine synthesis and which vitamin does it need?

Ornithine decarboxylase, which uses pyridoxal phosphate (vitamin B6).

## Which molecule donates the aminopropyl groups to make spermidine and spermine?

Decarboxylated S-adenosylmethionine.

## How does eflornithine act?

It is a suicide (irreversible) inhibitor of ornithine decarboxylase.

## How is ornithine decarboxylase degraded?

Antizyme binds it and delivers it to the 26S proteasome without ubiquitin tagging; its half-life is only minutes.

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Educational information, not medical advice. For any symptom, see a health professional.

Sources: [ODC1: Ornithine decarboxylase (human)](https://www.uniprot.org/uniprotkb/P11926/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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