Spermidine: the pathway in the body · Biomarker & Blood Analysis

This page shows the biochemical pathway behind the laboratory value Spermidine: which stations follow one another, which enzymes carry out each step and which cofactors they use. Every statement has a source. The page describes general textbook knowledge and says nothing about any individual person.

In brief

Spermidine belongs to the polyamines, small molecules carrying several positive charges. Cells build it from ornithine; it attaches to RNA and DNA and provides the piece from which the amino acid hypusine is formed on the factor eIF5A. Antizyme and SSAT keep its amount balanced.

The pathway step by step

Each station states what the compound does there. Three signs: ↑ supplies — builds up or makes available · ↓ depletes — inhibits, consumes or withholds · ↕ both, depending on amount. Behind it stands what the statement rests on: established physiology, observed in studies, or contested. The signs do not grade; they name the direction.

1. Ornithine → Putrescine ODC · vitamin B6 (PLP) Ornithine decarboxylase removes the carboxyl group from ornithine. The enzyme is made and broken down very quickly; this is how the cell regulates the amount of polyamines. When polyamines accumulate, the protein antizyme slows the enzyme. Source 1↑ supplies Putrescine is the first polyamine and the precursor of spermidine. When enough polyamines are present, the cell makes the protein antizyme; it sends ornithine decarboxylase to breakdown. established physiology Source 1
   ⚖ When the balance tips

   too much — When polyamines accumulate, the cell makes more antizyme; it slows ornithine decarboxylase and at the same time the uptake of polyamines from the surroundings.

   too little — If little putrescine is available, spermidine synthase has less starting material, and less spermidine is formed.

   established physiology · Source 1

2. Putrescine → Spermidine Spermidine synthase · dcSAM Spermidine synthase attaches an aminopropyl group from dcSAM to putrescine. Spermidine also comes from food, such as wheat germ, soybeans and aged cheese, and from gut bacteria. It is the building block for hypusine. Source 1, 5↑ supplies Spermidine is the precursor of spermine and at the same time the only donor for the modification of eIF5A: part of the spermidine becomes hypusine there. established physiology Source 1, 3
   ⚖ When the balance tips

   too much — If spermidine builds up, SSAT marks the excess with acetyl groups; it is then recycled or excreted.

   too little — If little spermidine is available, less eIF5A with hypusine is formed, and proteins with difficult stretches are made more slowly.

   established physiology · Source 1, 3

3. Spermidine → Spermine Spermine synthase · dcSAM A second aminopropyl group turns spermidine into spermine. Both polyamines carry several positive charges and therefore bind to negatively charged molecules. Recycling turns it back into spermidine. Source 1↑ supplies With its four charges, spermine binds nucleic acids even more tightly than spermidine. It also serves as a reserve: through recycling the cell recovers spermidine from it. established physiology Source 1
   ⚖ When the balance tips

   too much — If spermine builds up, the cell recycles it via SSAT and oxidases; the oxidation releases hydrogen peroxide and reactive aldehydes.

   too little — If little spermine is present, the return route to spermidine stays small, and the cell depends more on new synthesis and uptake.

   established physiology · Source 1

4. Spermine → Polyamine recycling SSAT, PAO · acetyl-CoA The enzyme SSAT attaches an acetyl group, and polyamine oxidase turns the product back into spermidine or putrescine. Acetylated forms leave the body in the urine. This releases hydrogen peroxide. Source 1↓ depletes Recycling draws spermine and spermidine from the pool: SSAT marks them, polyamine oxidase cleaves them. This releases hydrogen peroxide and an aldehyde. established physiology Source 1
   ⚖ When the balance tips

   too much — If SSAT works strongly, the pool of spermidine and spermine shrinks, and the oxidation releases more hydrogen peroxide and aldehydes.

   too little — If it works little, polyamines stay in the cell longer, and excess is released more slowly.

   established physiology · Source 1

5. SAM → dcSAM AdoMetDC The decarboxylase AdoMetDC removes the carboxyl group from SAM. The resulting dcSAM supplies the aminopropyl groups for spermidine and spermine. Spermidine slows its formation. Source 1↑ supplies dcSAM serves almost only the polyamine pathway. The cell keeps it scarce: putrescine activates AdoMetDC, while spermidine and spermine slow its formation. established physiology Source 1
   ⚖ When the balance tips

   too much — If plenty of dcSAM is present, the synthases convert more putrescine to spermidine and spermidine to spermine, as far as starting material is available.

   too little — If little dcSAM is available, putrescine accumulates, and less spermidine and spermine are formed.

   established physiology · Source 1

6. Spermidine in the cell → eIF5A with hypusine DHS, DOHH · oxygen Two enzymes transfer part of the spermidine to the factor eIF5A. This creates hypusine, an amino acid found only in this one protein. Only with hypusine is eIF5A active. Source 3↑ supplies eIF5A is active only with hypusine. The modification uses part of a spermidine molecule and NAD⁺; the second step needs iron and oxygen. established physiology Source 3
   ⚖ When the balance tips

   too much — Once eIF5A is fully modified, more spermidine brings no further modification; the amount of the factor sets the limit.

   too little — If little spermidine is available, more eIF5A remains unfinished, and less active factor is available to the ribosome.

   established physiology · Source 3

7. eIF5A with hypusine → Protein synthesis · ribosome With hypusine, eIF5A helps the ribosome past difficult stretches, such as runs of several prolines. Without this modification, protein synthesis stalls at exactly such stretches. With little spermidine, more eIF5A stays unfinished. Source 3↑ supplies With hypusine, eIF5A helps the ribosome form peptide bonds at difficult stretches and also takes part in finishing the protein chain. established physiology Source 3
   ⚖ When the balance tips

   too much — More active eIF5A does not speed up protein synthesis without limit; it acts only where the ribosome stalls.

   too little — If little active eIF5A is present, the ribosome pauses longer at proline runs, and proteins with such stretches are made more slowly.

   established physiology · Source 3

8. Spermidine in the cell → Binding to RNA and DNA Polyamines attach to nucleic acids and stabilise their folding. In this way they influence how RNA is read and how DNA is packaged. They do so by shielding negative charges. Source 1, 2↑ supplies Polyamines shield negative charges on nucleic acids. This keeps RNA folds stable and lets DNA be packed more densely. established physiology Source 1, 2
   ⚖ When the balance tips

   too much — If many polyamines attach, DNA is packed more densely in experiments, and it changes which RNA stretches are read.

   too little — If few polyamines are bound, RNA folds are less stable, and DNA is packed more loosely.

   observed in studies · Source 1, 2

9. Spermidine in the cell → Autophagy EP300 inhibited In cell and animal models, spermidine inhibits the acetyltransferase EP300. Autophagy proteins then remain unacetylated, and the cell begins to break down and recycle its own components. With little spermidine, this runs more slowly in models. Source 4, 2↑ supplies In cell and animal models, spermidine inhibits the acetyltransferase EP300; autophagy proteins stay unacetylated, and the cell breaks down more of its own components. eIF5A with hypusine is also involved. observed in studies Source 4, 2
   ⚖ When the balance tips

   too much — If spermidine rises in animal models, EP300 is inhibited more strongly, and more cell material is broken down and recycled; the effect depends on the amount.

   too little — If little spermidine is available, EP300 stays more active, autophagy proteins are acetylated, and the breakdown of the cell's own components runs more slowly in cell models.

   observed in studies · Source 4, 2

Further stations

• Ornithine — from arginine Spermidine is one of the polyamines. The starting point is ornithine, which arises from arginine in the urea cycle. How much of it moves on is set by the next enzyme. Source 1↑ supplies Ornithine is the starting material of all polyamines. How much of it becomes putrescine is set mainly by the amount of ornithine decarboxylase, not by the amount of ornithine. established physiology Source 1
  ⚖ When the balance tips

  too much — If plenty of ornithine is present, putrescine does not rise without limit: the rapidly turned-over ornithine decarboxylase restricts the flow.

  too little — If little ornithine is available, ornithine decarboxylase has less starting material, and the cell relies more on polyamines it takes up from outside.

  established physiology · Source 1

• SAM — S-adenosylmethionine SAM is the cell's central methyl group donor. A small part of it enters the polyamine pathway. Methylation and the polyamine pathway share the same pool. Source 1↑ supplies After decarboxylation, SAM supplies the aminopropyl groups. The rest of the molecule, methylthioadenosine, is recovered as methionine via a pathway of its own. established physiology Source 1
  ⚖ When the balance tips

  too much — If plenty of SAM is present, polyamine formation does not rise without limit; AdoMetDC is the limiting step.

  too little — If little SAM is available, methylation and the polyamine pathway share a smaller pool, and less dcSAM forms.

  established physiology · Source 1

• Spermidine in the cell — free and bound In the cell, spermidine is partly free and partly bound to RNA, DNA and membranes. Because of its positive charges, it attaches to negatively charged molecules. Only the free portion is available for conversion. Source 2, 1↑ supplies Spermidine acts through its charges: it covers negatively charged sites on RNA, DNA and membranes. Most of it is bound; only the free portion is available for conversion and signalling. established physiology Source 1, 2
  ⚖ When the balance tips

  too much — If free polyamines rise sharply, they become toxic to the cell; antizyme and SSAT then throttle synthesis and uptake and speed up recycling.

  too little — If little spermidine is in the cell, it makes more ornithine decarboxylase and takes up more polyamines from outside.

  established physiology · Source 1

Cofactors in this pathway

• Ornithine — Starting material from which ornithine decarboxylase makes putrescine; the amount of enzyme limits turnover Source 1In the ORY catalogue as a laboratory value: Ornithin
• Arginine — Amino acid from which ornithine arises in the urea cycle; raw material of all polyamines Source 1In the ORY catalogue as a laboratory value: Arginin
• Vitamin B6 — Cofactor (PLP) of ornithine decarboxylase; without PLP no putrescine forms Source 1In the ORY catalogue as a laboratory value: Vitamin B6
• SAM (from methionine) — Converted into dcSAM and thereby provides the aminopropyl group for spermidine and spermine; also feeds methylation Source 1In the ORY catalogue as a laboratory value: Methionin
• NAD⁺ — Cofactor of deoxyhypusine synthase, which transfers the spermidine part onto eIF5A; needed for active eIF5A Source 7, 3In the ORY catalogue as a laboratory value: NAD⁺ (Nicotinamidadenindinukleotid)
• Iron — Two iron atoms in the active site of deoxyhypusine hydroxylase, which completes the hypusine modification Source 8, 3In the ORY catalogue as a laboratory value: Eisen
• Acetyl-CoA — Donor of the acetyl group for SSAT during the breakdown of the polyamines; marks excess for excretion Source 1

What acts on this pathway

• Eflornithine — Eflornithine binds tightly to ornithine decarboxylase and switches it off permanently. This has been described for local application to the skin. Source 6

Sources

1. Pegg AE. Mammalian polyamine metabolism and function. IUBMB Life 2009 · PubMed 19603518
2. Madeo F, Eisenberg T, Pietrocola F et al. Spermidine in health and disease. Science 2018 · PubMed 29371440
3. Park MH, Wolff EC. Hypusine, a polyamine-derived amino acid critical for eukaryotic translation. J Biol Chem 2018 · PubMed 30257869
4. Hofer SJ, Simon AK, Bergmann M et al. Mechanisms of spermidine-induced autophagy and geroprotection. Nat Aging 2022 · PubMed 37118547
5. Zou D, Zhao Z, Li L et al. A comprehensive review of spermidine: Safety, health effects, absorption and metabolism, food materials evaluation, physical and chemical processing, and bioprocessing. Compr Rev Food Sci Food Saf 2022 · PubMed 35478379
6. Balfour JA, McClellan K. Topical eflornithine. Am J Clin Dermatol 2001 · PubMed 11705097
7. Chen M, Gai Z, Okada C et al. Flexible NAD(+) Binding in Deoxyhypusine Synthase Reflects the Dynamic Hypusine Modification of Translation Factor IF5A. Int J Mol Sci 2020 · PubMed 32752130
8. Frey AG, Nandal A, Park JH et al. Iron chaperones PCBP1 and PCBP2 mediate the metallation of the dinuclear iron enzyme deoxyhypusine hydroxylase. Proc Natl Acad Sci U S A 2014 · PubMed 24843120

Related pathways

• Methylation: methionine and homocysteine — sam
• Arginine and nitric oxide — ornithine
• Vitamin B12 — sam
• Carnitine — Vitamin B6, Methionin
• Dopamine, noradrenaline, adrenaline — Vitamin B6, Methionin

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert approval pending
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