Tyrosine

Tyrosine
Systematic name	(S)-2-Amino-3-(4-hydroxy- phenyl)-propanoic acid
Abbreviations	Tyr Y
Chemical formula	C9H11NO3
Molecular mass	181.19 g mol-1
Melting point	343 °C
Density	1.456 g cm-3
Isoelectric point	5.66
pKa	2.24 9.04 10.10
Molar extinction coefficient	1420 M-1 cm-1 at 274.6 nm
PubChem	1153
CAS number	[60-18-4]
EINECS number	200-460-4
SMILES	N[C@@H](Cc1ccc(O)cc1)C(O)=O
Absorption and emission spectrum Absorbance and fluorescence of tyrosine in water/buffer
Disclaimer and references

Tyrosine (from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in cheese), 4-hydroxyphenylalanine, or 2-amino-3(4-hydroxyphenyl)-propanoic acid, is one of the 20 amino acids that are used by cells to synthesize proteins. It has a phenol side chain with a hydroxyl group. Upon the location of the hydroxyl group, there are three structural isomers of Tyr, namely para-Tyr (p-Tyr), meta-Tyr (m-Tyr) and ortho-Tyr (o-Tyr). Enzymatically, only the first isomer (p-Tyr) is produced from L-Phe by the Phe-hydroxylase enzyme. The other two isoforms, m-Tyr and o-Tyr can be produced as a consequence of free radical attack on Phe in states with increased oxidative stress.

tyrosine molecule

Tyrosine is converted to levodopa by tyrosine hydroxylase, an enzyme.

Some of the tyrosine residues can be tagged with a phosphate group (phosphorylated) by protein kinases. (In its phosphorylated state, it is referred to as phosphotyrosine.). Tyrosine phosphorylation is considered as one of the key steps in signal transduction and regulation of enzymatic activity. Phosphotyrosine can be detected through specific antibodies. Tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation. Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase (TPST). Like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine. Tyrosine is also precursor to the thyroid hormones thyroxine and triiodothyronine, the pigment melanin, and the biologically-active catecholamines dopamine, norepinephrine and epinephrine.

In Papaver somniferum, the opium poppy, it is used to produce morphine.

Biosynthesis

Tyrosine cannot be completely synthesized by animals, although it can be made by hydroxylation of phenylalanine if the latter is in abundant supply. It is produced by plants and most microorganisms from prephenate, an intermediate on the shikimate pathway.

Prephenate is oxidatively decarboxylated with retention of the hydroxyl group to give p-hydroxyphenylpyruvate. This is transaminated using glutamate as the nitrogen source to give tyrosine and α-ketoglutarate.

Tyrosine hydroxylase

Tyrosine hydroxylase (TH) is the rate-limiting enzyme involved in the synthesis of the catecholamines such as dopamine, norepinephrine and epinephrine.

Medical use

L-Tyrosine is sometimes recommended by practitioners as helpful for weight loss, clinical depression, Parkinson's Disease, and phenylketonuria; however, one study found that it had no impact on endurance exercise performance.

See also

• Tyramine
• Alkaptonuria
• Tyrosinemia
• Albinism
• Tyrosine sulfation

References

ISBN links support NWE through referral fees

• AJ Hoffhines et al. Journal of Biological Chemistry 281:37877-37887, 2006[1]
• GA Molnar et al. Kidney International 68:2281-2287, 2005 Abstract
• GA Molnar et al. Free Radical Research 39(12):1359-1366, 2005 Abstract

External links

• Phenylalanine and tyrosine biosynthesis
• Computational Chemistry Wiki
• Phosphotyrosine Antibody

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