[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Biochemistry](https://durgical.com/en/biochemistry/) › Protoporphyrin IX

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

# Protoporphyrin IX

Protoporphyrin IX is the heme ring before it receives iron; it is red, fluorescent and builds up in protoporphyria.

Updated 2026-11-01

Loading the 3D model…

## Key facts

- It is the substrate of ferrochelatase, the last step of heme synthesis.
- It is hydrophobic: it does not appear in urine; it is excreted in bile and stool.
- It absorbs violet light (around 405 nm) and gives off red fluorescence; with light it generates reactive oxygen species.
- With zinc instead of iron it forms zinc protoporphyrin (iron deficiency, lead).

**Formula**
C₃₄H₃₄N₄O₄

**PubChem**
[CID 4971](https://pubchem.ncbi.nlm.nih.gov/compound/4971)

## Structure

- Porphyrin ring with four methyls, two vinyls and two propionates; IX names the order of those groups, the only one nature uses.

## Clinical notes

- Erythropoietic protoporphyria: high free protoporphyrin in red cells; burning pain in sunlight and risk of gallstones and liver damage.
- Fluorescence-guided surgery: oral 5-ALA makes glioma cells accumulate protoporphyrin IX and glow red.
- Photodynamic therapy: topical ALA plus light destroys actinic keratoses and some superficial skin cancers.

## Pathways

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

## Related conditions

- [Erythropoietic protoporphyria](https://durgical.com/en/conditions/erythropoietic-protoporphyria/)
- [Lead poisoning](https://durgical.com/en/conditions/lead-poisoning/)
- [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/)

## Related

- [Ferrochelatase](https://durgical.com/en/biochemistry/enzymes/ferrochelatase/)
- [Heme](https://durgical.com/en/biochemistry/molecules/heme/)
- [δ-Aminolevulinic acid (ALA)](https://durgical.com/en/biochemistry/molecules/aminolevulinic-acid/)
- [Uroporphyrinogen decarboxylase](https://durgical.com/en/biochemistry/enzymes/uroporphyrinogen-decarboxylase/)

## Test yourself

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

## Why does protoporphyrin not appear in urine in protoporphyria?

It is hydrophobic: it leaves through bile, so urine porphyrins are normal.

## What forms when protoporphyrin IX receives zinc instead of iron?

Zinc protoporphyrin, which rises in iron deficiency and lead poisoning.

## How is protoporphyrin IX used in glioma surgery?

5-ALA is given; the tumour accumulates protoporphyrin IX, which fluoresces red under violet light and marks the margins.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/biochemistry/molecules/protoporphyrin-ix/)

Molecules are shown in their neutral form, as the databases deposit them; in the cell the acids and phosphates are ionised.

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

Sources: [Protoporphyrin IX (CID 4971)](https://pubchem.ncbi.nlm.nih.gov/compound/4971) (PubChem, NCBI, 2026) · Public domain; [Porphyrins blood test: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/003372.htm) (MedlinePlus, US National Library of Medicine, 2026); [FECH gene: MedlinePlus Genetics](https://medlineplus.gov/genetics/gene/fech/) (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).

[← All of biochemistry](https://durgical.com/en/biochemistry/)

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

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