Ornithine loses CO₂ to give putrescine, then two aminopropyl groups are added in turn
Route: Ornithine → Putrescine + dcSAM → Spermidine + dcSAM → Spermine
Ornithine decarboxylase, which needs pyridoxal phosphate, removes the carboxyl group of ornithine and leaves putrescine. Spermidine synthase moves an aminopropyl group from decarboxylated SAM onto one amino group of putrescine, and spermine synthase does the same to spermidine. Each step releases 5'-methylthioadenosine. Polyamines are cations in the cell and bind DNA and RNA.
Practice this pathway All pathways
| Step | Enzyme | EC | In | Out |
|---|---|---|---|---|
| 1 | Ornithine decarboxylase | 4.1.1.17 | CO₂ | |
| 2 | Spermidine synthase | 2.5.1.16 | MTA | |
| 3 | Spermine synthase | 2.5.1.22 | MTA |
Enzyme names and EC numbers are those used on the interactive board. Checked against sources: see the claim table in the repository (tools/pathway_data/checks).