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

# Molecules derived from amino acids

Besides building proteins, amino acids give hormones, neurotransmitters, pigments and key molecules such as nitric oxide, creatine and haem.

Updated 2026-11-01

## Key facts

- Tyrosine → catecholamines (dopamine, noradrenaline, adrenaline), melanin and thyroid hormones.
- Tryptophan → serotonin, melatonin and niacin; histidine → histamine; glutamate → GABA.
- Arginine → nitric oxide, creatine (with glycine and SAM), urea and polyamines (via ornithine).
- Glycine → haem (with succinyl-CoA), creatine, glutathione and bile acid conjugation.
- The decarboxylases that make dopamine, serotonin, histamine and GABA use pyridoxal phosphate (B6).

## In detail

- Catecholamines: tyrosine → L-DOPA (tyrosine hydroxylase, BH4) → dopamine (DOPA decarboxylase, B6) → noradrenaline (dopamine β-hydroxylase, vitamin C and copper) → adrenaline (PNMT, SAM; induced by cortisol).
- Serotonin and melatonin: tryptophan → 5-hydroxytryptophan (tryptophan hydroxylase, BH4) → serotonin (B6) → N-acetylserotonin → melatonin in the pineal gland.
- Niacin: tryptophan passes through kynurenine and forms NAD⁺; the route needs B6 and B2.
- Histamine: histidine decarboxylase (B6) makes it in mast cells, basophils and stomach cells.
- GABA: glutamate decarboxylase (B6) makes it in inhibitory neurons.
- Nitric oxide: nitric oxide synthase (BH4, NADPH) turns arginine into citrulline and NO, which relaxes smooth muscle via cGMP.
- Creatine: arginine + glycine → guanidinoacetate (kidney); SAM methylates it in the liver; muscle phosphorylates it, and its product creatinine is excreted at a nearly constant rate.

## Clinical notes

- Phaeochromocytoma: excess catecholamines; metanephrines are measured.
- Carcinoid tumour: excess serotonin; urinary 5-HIAA is measured.
- Blood creatinine is used to estimate glomerular filtration.
- B6 deficiency can cause seizures (less GABA) and anaemia (less haem).

## Pathways

- [Catecholamine synthesis and breakdown](https://durgical.com/en/biochemistry/pathways/catecholamine-synthesis-and-breakdown/)
- [Serotonin and melatonin synthesis](https://durgical.com/en/biochemistry/pathways/serotonin-and-melatonin-synthesis/)

## Related conditions

- [Phaeochromocytoma](https://durgical.com/en/conditions/phaeochromocytoma/)
- [Carcinoid syndrome](https://durgical.com/en/conditions/carcinoid-syndrome/)
- [Parkinson disease](https://durgical.com/en/conditions/parkinson-disease/)
- [Hartnup disease](https://durgical.com/en/conditions/hartnup-disease/)
- [Oculocutaneous albinism](https://durgical.com/en/conditions/oculocutaneous-albinism/)

## Related

- [Tyrosine](https://durgical.com/en/biochemistry/molecules/tyrosine/)
- [Tryptophan](https://durgical.com/en/biochemistry/molecules/tryptophan/)
- [Glutamate (glutamic acid)](https://durgical.com/en/biochemistry/molecules/glutamate/)
- [Tyrosine hydroxylase](https://durgical.com/en/biochemistry/enzymes/tyrosine-hydroxylase/)
- [Tetrahydrobiopterin (BH4)](https://durgical.com/en/biochemistry/molecules/tetrahydrobiopterin/)
- [S-adenosylmethionine (SAM)](https://durgical.com/en/biochemistry/molecules/s-adenosylmethionine/)
- [NAD⁺ (nicotinamide adenine dinucleotide)](https://durgical.com/en/biochemistry/molecules/nad/)

## Test yourself

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

## Which enzyme turns noradrenaline into adrenaline, and which donor does it use?

Phenylethanolamine N-methyltransferase (PNMT), with SAM as methyl donor; cortisol induces it in the adrenal medulla.

## Which amino acid gives rise to nitric oxide?

Arginine; nitric oxide synthase turns it into citrulline and NO.

## Which vitamin do the dopamine, serotonin, histamine and GABA decarboxylases share?

B6, as pyridoxal phosphate.

## Which urinary metabolite is measured to look for a carcinoid tumour?

5-Hydroxyindoleacetic acid (5-HIAA), the breakdown product of serotonin.

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

Sources: [Catecholamine biosynthesis](https://reactome.org/PathwayBrowser/#/R-HSA-209905) (Reactome, 2026); [Serotonin and melatonin biosynthesis](https://reactome.org/PathwayBrowser/#/R-HSA-209931) (Reactome, 2026); [Creatine metabolism](https://reactome.org/PathwayBrowser/#/R-HSA-71288) (Reactome, 2026); [Histidine catabolism](https://reactome.org/PathwayBrowser/#/R-HSA-70921) (Reactome, 2026); [GABA synthesis, release, reuptake and degradation](https://reactome.org/PathwayBrowser/#/R-HSA-888590) (Reactome, 2026).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/biochemistry/topics/molecules-derived-from-amino-acids/