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

# Uroporphyrinogen decarboxylase

Uroporphyrinogen decarboxylase removes four carboxyls from the ring; when it fails in the liver, porphyria cutanea tarda appears.

Updated 2026-11-01

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## Key facts

- Uroporphyrinogen III → coproporphyrinogen III + 4 CO₂, in the cytosol.
- It decarboxylates the four acetate side chains (turning them into methyls) in order, with no cofactors or metals.
- It is a dimer; structure 1R3Y shows the product, coproporphyrinogen III, in the active-site cleft.
- In an iron-loaded liver an inhibitor (uroporphomethene) forms from the substrate itself.

**Also called**
UROD

**EC number**
[4.1.1.37](https://www.enzyme-database.org/query.php?ec=4.1.1.37)

**Genes**
UROD

**Structure (PDB)**
[1R3Y](https://www.rcsb.org/structure/1R3Y)

## Regulation

- Liver iron, alcohol, estrogens, smoking and hepatitis C favour the oxidative stress that inhibits it.

## Inhibitors and toxins

- Uroporphomethene (formed with iron and oxidation)
- Hexachlorobenzene and dioxins

## Clinical notes

- Porphyria cutanea tarda: most cases are acquired (type 1); about a quarter carry a heterozygous UROD mutation (type 2).
- Two mutated copies cause hepatoerythropoietic porphyria, severe and starting in childhood.
- Uroporphyrin and seven-carboxyl porphyrins build up in urine, which looks pinkish and fluoresces under Wood light.

## Pathways

- [Heme synthesis](https://durgical.com/en/biochemistry/pathways/heme-synthesis/)

## Related conditions

- [Porphyria cutanea tarda](https://durgical.com/en/conditions/porphyria-cutanea-tarda/)
- [Hereditary hemochromatosis](https://durgical.com/en/conditions/hereditary-hemochromatosis/)
- [Viral hepatitis](https://durgical.com/en/conditions/viral-hepatitis/)

## Related

- [Porphobilinogen deaminase](https://durgical.com/en/biochemistry/enzymes/porphobilinogen-deaminase/)
- [Ferrochelatase](https://durgical.com/en/biochemistry/enzymes/ferrochelatase/)
- [Protoporphyrin IX](https://durgical.com/en/biochemistry/molecules/protoporphyrin-ix/)
- [Iron metabolism](https://durgical.com/en/biochemistry/topics/iron-metabolism/)

## Test yourself

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

## Which porphyria results from low liver uroporphyrinogen decarboxylase activity?

Porphyria cutanea tarda, the most common, with blisters on sun-exposed skin.

## Why does iron overload worsen porphyria cutanea tarda?

Iron promotes oxidation of the substrate to uroporphomethene, which inhibits the enzyme; that is why phlebotomy helps.

## Which chemical groups does this enzyme remove?

Four carboxyls from the acetate side chains, which are left as methyls.

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

Sources: [UROD: Uroporphyrinogen decarboxylase (human)](https://www.uniprot.org/uniprotkb/P06132/entry) (UniProt, 2026); [UROD gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/urod/) (MedlinePlus, US National Library of Medicine, 2026); [1R3Y: Uroporphyrinogen Decarboxylase in complex with coproporphyrinogen-III](https://www.rcsb.org/structure/1R3Y) (RCSB Protein Data Bank, 2026); [Porphyria: MedlinePlus Genetics](https://medlineplus.gov/genetics/condition/porphyria/) (MedlinePlus, US National Library of Medicine, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/enzymes/uroporphyrinogen-decarboxylase/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/enzymes/uroporphyrinogen-decarboxylase/