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

# Tyrosine

Tyrosine comes from phenylalanine and is the starting point of dopamine, adrenaline, melanin and thyroid hormones.

Updated 2026-11-01

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## Key facts

- Non-essential while phenylalanine hydroxylase works; essential in phenylketonuria.
- Tyrosine hydroxylase → L-DOPA → dopamine → noradrenaline → adrenaline.
- Tyrosinase turns it into melanin in melanocytes.
- In the thyroid, tyrosine residues of thyroglobulin are iodinated to form T3 and T4.
- It is broken down to fumarate and acetoacetate.

**Formula**
C₉H₁₁NO₃

**PubChem**
[CID 6057](https://pubchem.ncbi.nlm.nih.gov/compound/6057)

## Structure

- Like phenylalanine with a hydroxyl on the ring (a phenol); in proteins that OH can be phosphorylated.

## Clinical notes

- Albinism (tyrosinase), alkaptonuria and the tyrosinaemias are defects of its metabolism.
- Phaeochromocytoma and neuroblastoma make excess catecholamines from it.
- In phenylketonuria tyrosine is short: lighter skin and hair from less melanin.

## Pathways

- [Phenylalanine and tyrosine metabolism](https://durgical.com/en/biochemistry/pathways/phenylalanine-and-tyrosine-metabolism/)
- [Catecholamine synthesis and breakdown](https://durgical.com/en/biochemistry/pathways/catecholamine-synthesis-and-breakdown/)

## Related conditions

- [Tyrosinaemia type I (hepatorenal)](https://durgical.com/en/conditions/tyrosinaemia-type-i/)
- [Alkaptonuria](https://durgical.com/en/conditions/alkaptonuria/)
- [Oculocutaneous albinism](https://durgical.com/en/conditions/oculocutaneous-albinism/)
- [Phaeochromocytoma](https://durgical.com/en/conditions/phaeochromocytoma/)
- [Hypothyroidism](https://durgical.com/en/conditions/hypothyroidism/)

## Related

- [Phenylalanine](https://durgical.com/en/biochemistry/molecules/phenylalanine/)
- [Tyrosine hydroxylase](https://durgical.com/en/biochemistry/enzymes/tyrosine-hydroxylase/)
- [Phenylalanine hydroxylase (PAH)](https://durgical.com/en/biochemistry/enzymes/phenylalanine-hydroxylase/)
- [Molecules derived from amino acids](https://durgical.com/en/biochemistry/topics/molecules-derived-from-amino-acids/)

## Test yourself

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

## What is the rate-limiting step of catecholamine synthesis from tyrosine?

Tyrosine hydroxylase, which makes L-DOPA with BH4, oxygen and iron.

## Why do people with phenylketonuria often have light skin and hair?

They have little tyrosine, and high phenylalanine inhibits tyrosinase, so less melanin is made.

## Which hormones are made from tyrosine residues in the thyroid?

T3 and T4, when tyrosine residues of thyroglobulin are iodinated and coupled.

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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: [L-Tyrosine (CID 6057)](https://pubchem.ncbi.nlm.nih.gov/compound/6057) (PubChem, NCBI, 2026) · Public domain; [Tyrosine catabolism](https://reactome.org/PathwayBrowser/#/R-HSA-8963684) (Reactome, 2026); [Catecholamine biosynthesis](https://reactome.org/PathwayBrowser/#/R-HSA-209905) (Reactome, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/biochemistry/molecules/tyrosine/
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