One of the 20 amino acids that make up proteins. It contains an aromatic ring as part of its side chain.



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Tyrosine (C₉H₁₁NO₃)


Molar mass: 181.19 g/mol

Melting point: 343 °C (649.4 °F)

Density: 1.456 g/cm³ (0.0526 lb/in³)


Tyrosine is a non-essential amino acid; it can be produced by the human body. It is an aromatic amino acid that forms colorless, fine, silky needles. It is poorly soluble in water and insoluble in alcohol and ether.

Its presence can be determined with the xanthoproteic reaction.

Occurrence and production

Tyrosine is a proteinogenic amino acid; it can also be found in its free form. Casein (or milk protein) is a particularly rich source of it.

Tyrosine is usually synthesized through hydrolysis of proteins. Biosynthesis of tyrosine proceeds from phenylalanine.


Tyrosine is the precursor of melanin, the pigment found in our skin. It is also the precursor of the neurotransmitter hormones norepinephrine and epinephrine. It is used in pharmaceuticals and dietary supplements.

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Amino acids

Amino acids are the monomers of proteins.

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