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Biochemistry · Topic

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.

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) (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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