PubChem = 1153
CAS = 60-18-4
SMILES = N [C@@H] (Cc1ccc(O)cc1)C(O)=O
C=9 | H=11 | N=1 | O=3
Tyrosine (abbreviated as Tyr or Y) [cite web | author=IUPAC-IUBMB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology
year = 1983 | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17] or 4-hydroxyphenylalanine, is one of the 20
amino acids that are used by cells to synthesize proteins. This is a non-essential amino acidand it is found in casein. In fact, the word "tyrosine" is from the Greek "tyros", meaning " cheese", as it was first discovered in 1846 by German chemist Justus von Liebigin the protein casein from cheese.cite web | url = http://www.infoplease.com/ce6/sci/A0849873.html | title = Tyrosine | author = | authorlink = | coauthors = | date = 2007 | format = | work = The Columbia Electronic Encyclopedia, 6th ed | publisher = Infoplease.com — Columbia University Press | pages = | language = | archiveurl = | archivedate = | quote = | accessdate = 2008-04-20] cite web | url = http://www.etymonline.com/index.php?term=tyrosine | title = Tyrosine | author = Douglas Harper | authorlink = | coauthors = | date = 2001 | format = | work = Online Etymology Dictionary | publisher = | pages = | language = | archiveurl = | archivedate = | quote = | accessdate = 2008-04-20]
Aside from being a proteogenic amino acid, tyrosine has a special role by virtue of the
phenolfunctionality. It occurs in proteins that are part of signal transductionprocesses. It functions as a receiver of phosphate groups that are transferred by way of protein kinases (so-called receptor tyrosine kinases). Phosphorylation of the hydroxyl group changes the activity of the target protein.
A tyrosine residue also plays an important role in
photosynthesis. In chloroplasts ( photosystem II), it acts as an electron donor in the reductionof oxidized chlorophyll. In this process, it undergoes deprotonationof its phenolic OH-group. This radical is subsequently reduced in the photosystem II by the four core manganese cluster.
In plants and most microorganisms, tyr is produced via prephenate, an intermediate on the shikimate pathway. Prephenate is oxidatively decarboxylated with retention of the
hydroxylgroup to give "p"-hydroxyphenylpyruvate, which is transaminated using glutamate as the nitrogen source to give tyrosine and α-ketoglutarate. Mammalssynthesize tyrosine from the essential amino acid phenylalanine(phe), which is derived from food. The conversion of phe to tyr is catalyzed by the enzyme phenylalanine hydroxylase, a monooxygenase. This enzyme catalyzes the reaction causing the addition of an hydroxyl group to the end of the 6-carbon aromatic ring of phenylalanine, such that it becomes tyrosine.
Phosphorylation and sulfation
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 to be 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.cite journal | author = Hoffhines AJ, Damoc E, Bridges KG, Leary JA, Moore KL | title = Detection and purification of tyrosine-sulfated proteins using a novel anti-sulfotyrosine monoclonal antibody | journal = J. Biol. Chem. | volume = 281 | issue = 49 | pages = 37877–87 | year = 2006 | pmid = 17046811 | doi = 10.1074/jbc.M609398200 ] Tyrosine sulfationis catalyzed by tyrosylprotein sulfotransferase (TPST). Like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine.
Precursor to hormones
adrenal gland, tyrosine is converted to levodopaby the enzyme tyrosine hydroxylase(TH). TH is also the rate-limiting enzymeinvolved in the synthesis of the catecholamine hormones dopamine, norepinephrine(noradrenaline), and epinephrine.
thyroidhormones triiodothyronine(T3) and thyroxine(T4) in the colloidof the thyroidalso are derived from tyrosine.
Precursor to alkaloids
Papaver somniferum", the opium poppy, tyrosine is used to produce the alkaloid morphine.
Precursor to pigments
Tyrosine is also the precursor to the pigment "
The decomposition of L-tyrosine (syn. "para"-hydroxyphenylalanine) begins with an α-ketoglutarate dependent
transaminationthrough the tyrosine transaminase to "para"-hydroxyphenyl pyruvate. The positional description "para", abbreviated "p", mean that the hydroxyl group and side chain on the phenyl ring are across from each other (see the illustration below). The next oxidation step catalyzes by "p"-hydroxylphenylpyruvate-dioxygenase and splitting off CO2 homogentisate (2,5-dihydroxyphenyl-1-acetate). In order to split the aromatic ring of homogentisate, a further dioxygenase, homogentistate-oxygenase is required. Thereby, through the incorporation of a further O2 molecule, maleylacetoacetate is created. Fumarylacetate is created maleylacetoacetate-"cis"-"trans"-isomerase through rotation of the carboxyl group created from the hydroxyl group via oxidation. This "cis-trans"-isomerase contains glutathioneas a coenzyme. Fumarylacetoacetate is finally split via fumarylacetoacetate-hydrolase through the addition of a water molecule.
fumarate(also a metabolite of the citric acid cycle) and acetoacetate (3-ketobutyroate) are liberated. Acetoacetate is a ketone body, which is activated with succinyl-CoA, and thereafter it can be converted into acetyl-CoAwhich in turn can be oxidized by the citric acid cycleor be used for fatty acid synthesis.
Ortho- and meta-tyrosine
isomers of tyrosine are known. In addition to common amino acid L-tyrosine which is the para isomer("para"-tyr, "p"-tyr or 4-hydroxyphenylalanine) there are two additional regioisomers, namely "meta"-tyrosine ("m"-tyr or 3-hydroxyphenylalanine or L-m-tyrosine) and "ortho"-tyrosine ("o"-tyr or 2-hydroxyphenylalanine) which occur in nature. The "m"-tyr and "o"-tyr isomers, which are rare, arise through non-enzymatic free-radicalhydroxylation of phenylalanine under conditions of oxidative stress.cite journal | author = Molnár GA, Wagner Z, Markó L, Kó Szegi T, Mohás M, Kocsis B, Matus Z, Wagner L, Tamaskó M, Mazák I, Laczy B, Nagy J, Wittmann I | title = Urinary ortho-tyrosine excretion in diabetes mellitus and renal failure: evidence for hydroxyl radical production | journal = Kidney Int. | volume = 68 | issue = 5 | pages = 2281–7 | year = 2005 | pmid = 16221230 | doi = 10.1111/j.1523-1755.2005.00687.x ] cite journal | author = Molnár GA, Nemes V, Biró Z, Ludány A, Wagner Z, Wittmann I | title = Accumulation of the hydroxyl free radical markers meta-, ortho-tyrosine and DOPA in cataractous lenses is accompanied by a lower protein and phenylalanine content of the water-soluble phase | journal = Free Radic. Res. | volume = 39 | issue = 12 | pages = 1359–66 | year = 2005 | pmid = 16298866 | doi = 10.1080/10715760500307107 ]
m-Tyrosine and analogues (rare in nature and therefore available synthetically) have shown application in
Parkinson's Disease, Alzheimer's diseaseand arthritis["Optimized Synthesis of L-m-Tyrosine Suitable for Chemical Scale-Up" Cara E. Humphrey, Markus Furegati, Kurt Laumen, Luigi La Vecchia, Thomas Leutert, J. Constanze D. Müller-Hartwieg, and Markus Vögtle Organic Process Research & Development 2007, 11, 1069–1075 DOI|10.1021/op700093y] .
Tyrosine is a starting material for
neurotransmitters and increases plasma neurotransmitter levels (particularly dopamine and norepinephrine)cite journal | author = Rasmussen DD, Ishizuka B, Quigley ME, Yen SS | title = Effects of tyrosine and tryptophan ingestion on plasma catecholamine and 3,4-dihydroxyphenylacetic acid concentrations | journal = J. Clin. Endocrinol. Metab. | volume = 57 | issue = 4 | pages = 760–3 | year = 1983 | pmid = 6885965 | doi = | issn = ] but has little if any effect on mood.cite journal |author=Leathwood PD, Pollet P |title=Diet-induced mood changes in normal populations |journal=Journal of psychiatric research |volume=17 |issue=2 |pages=147–54 |year=1982 |pmid=6764931 |doi=] cite journal |author=Deijen JB, Orlebeke JF |title=Effect of tyrosine on cognitive function and blood pressure under stress |journal = Brain Res. Bull. | volume = 33 |issue = 3 |pages = 319–23 |year=1994 | pmid=8293316| doi = 10.1016/0361-9230(94)90200-3 ] cite journal |author=Lieberman HR, Corkin S, Spring BJ, Wurtman RJ, Growdon JH |title=The effects of dietary neurotransmitter precursors on human behavior |journal=Am J Clin Nutr. |volume=42 |issue=2 |pages=366–370 |year=1985 |pmid=4025206 ] The effect on mood is more noticeable in humans subjected to stressful conditions (see below).
A number of studies have found tyrosine to be useful during conditions of stress, cold, fatigue,cite journal | author = Hao S, Avraham Y, Bonne O, Berry EM | title = Separation-induced body weight loss, impairment in alternation behavior, and autonomic tone: effects of tyrosine | journal = Pharmacol. Biochem. Behav. | volume = 68 | issue = 2 | pages = 273–81 | year = 2001 | pmid = 11267632 | doi = 10.1016/S0091-3057(00)00448-2 ] prolonged work and sleep deprivation,cite journal | author = Magill RA, Waters WF, Bray GA, Volaufova J, Smith SR, Lieberman HR, McNevin N, Ryan DH | title = Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation | journal = Nutritional Neuroscience | volume = 6 | issue = 4 | pages = 237–46 | year = 2003 | pmid = 12887140 | doi = | issn = ] cite journal | author = Neri DF, Wiegmann D, Stanny RR, Shappell SA, McCardie A, McKay DL | title = The effects of tyrosine on cognitive performance during extended wakefulness | journal = Aviation, space, and environmental medicine | volume = 66 | issue = 4 | pages = 313–9 | year = 1995 | pmid = 7794222 | doi = | issn = ] with reductions in stress hormone levels,cite journal |author=Reinstein DK, Lehnert H, Wurtman RJ |title=Dietary tyrosine suppresses the rise in plasma corticosterone following acute stress in rats |journal=Life Sci. |volume=37 |issue=23 |pages=2157–63 |year=1985 |pmid=4068899| doi = 10.1016/0024-3205(85)90566-1 ] reductions in stress-induced weight loss seen in animal trials,cite journal |author=Hao S, Avraham Y, Bonne O, Berry EM |title=Separation-induced body weight loss, impairment in alternation behavior, and autonomic tone: effects of tyrosine |journal=Pharmacol. Biochem. Behav. |volume=68 |issue=2 |pages=273–81 |year=2001 |pmid=11267632| doi = 10.1016/S0091-3057(00)00448-2 ] improvements in cognitive and physical performancecite journal |author=Deijen JB, Wientjes CJ, Vullinghs HF, Cloin PA, Langefeld JJ |title=Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course |journal=Brain Res. Bull. |volume=48 |issue=2 |pages=203–9 |year=1999 |pmid=10230711| doi = 10.1016/S0361-9230(98)00163-4 ] cite journal |author=Mahoney CR, Castellani J, Kramer FM, Young A, Lieberman HR |title=Tyrosine supplementation mitigates working memory decrements during cold exposure |journal=Physiology and Behavior |volume=IN PRESS |issue= | pages = 575|year=2007 |pmid=17585971 |doi=10.1016/j.physbeh.2007.05.003] seen in human trials. Because tyrosine hydroxylase is the rate limiting enzyme, however, effects are less significant than those of
Tyrosine does not seem to have any significant effect on mood, cognitive or physical performance in normal circumstances.cite journal | author = Chinevere TD, Sawyer RD, Creer AR, Conlee RK, Parcell AC | title = Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance | journal = J. Appl. Physiol. | volume = 93 | issue = 5 | pages = 1590–7 | year = 2002 | pmid = 12381742 | doi = 10.1152/japplphysiol.00625.2001 | doi_brokendate = 2008-06-25 ] cite journal | author = Strüder HK, Hollmann W, Platen P, Donike M, Gotzmann A, Weber K | title = Influence of paroxetine, branched-chain amino acids and tyrosine on neuroendocrine system responses and fatigue in humans | journal = Horm. Metab. Res. | volume = 30 | issue = 4 | pages = 188–94 | year = 1998 | pmid = 9623632 | doi = | issn = ] cite journal | author = Thomas JR, Lockwood PA, Singh A, Deuster PA | title = Tyrosine improves working memory in a multitasking environment | journal = Pharmacol. Biochem. Behav. | volume = 64 | issue = 3 | pages = 495–500 | year = 1999 | pmid = 10548261| doi = 10.1016/S0091-3057(99)00094-5 ] A daily dosage supported in the literature is about 100 mg/kg for an adult. [cite web |author=Gelenberg, A.J., Wojcik, J.D., Growdon, J.H., Sved, A.F., and Wurtman, R.J. |title=Tyrosine for the Treatment of Depression |url=http://wurtmanlab.mit.edu/publications/pdf/456.pdf |format=PDF |accessdate=2008-03-25 ] The usual dosage amounts to 500-1500 mg per day (dose suggested by most manufacturers; usually an equivalent to 1-3 capsules of pure tyrosine). It is not recommended to exceed 12000 mg (12 g) per day. In fact, too high doses result in reduced levels of dopamine.cite journal | author = Chinevere TD, Sawyer RD, Creer AR, Conlee RK, Parcell AC | title = Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance | journal = J. Appl. Physiol. | volume = 93 | issue = 5 | pages = 1590–7 | year = 2002 | pmid = 12381742 | doi = 10.1152/japplphysiol.00625.2001 | doi_brokendate = 2008-06-25 ] Tyrosine may decrease the absorption of other amino acids in high or chronic doses. It decreases absorption of l-dopa.
* [http://www.genome.jp/kegg/pathway/map/map00350.html Tyrosine metabolism]
* [http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/AminoAcid/PheTyr.html Phenylalanine and tyrosine biosynthesis]
* [http://www.genome.jp/kegg/pathway/map/map00400.html Phenylalanine, Tyrosine, and tryptophan biosynthesis]
* [http://www.compchemwiki.org/index.php?title=Tyrosine Computational Chemistry Wiki]
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