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Skeletal formula of tyrosine
3D stick model of tyrosine molecule

Tyrosine

Systematic (IUPAC) name
(S)-2-Amino-3-(4-hydroxyphenyl)-propanoic acid
Identifiers
CAS number60-18-4
PubChem        1153
Chemical data
FormulaC9H11NO3 
Molar mass181. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Molar mass, symbol M, is the Mass of one mole of a substance ( Chemical element or Chemical compound) 19 g/mol
SMILESN[C@@H](Cc1ccc(O)cc1)C(O)=O
Complete data

Tyrosine (abbreviated as Tyr or Y)[1] or 4-hydroxyphenylalanine, is one of the 20 amino acids that are used by cells to synthesize proteins. In Chemistry, an amino acid is a Molecule containing both Amine and Carboxyl Functional groups In Biochemistry, this The cell is the structural and functional unit of all known living Organisms It is the smallest unit of an organism that is classified as living and is often called Protein biosynthesis (synthesis is the process in which cells build Proteins The term is sometimes used to refer only to protein translation but more Proteins are large Organic compounds made of Amino acids arranged in a linear chain and joined together by Peptide bonds between the Carboxyl This is a non-essential amino acid and it is found in large quantities in casein. An essential amino acid or indispensable amino acid is an Amino acid that cannot be synthesized de novo by the organism (usually referring to See Casein paint for information about casein usage in artistic painting In fact, the word "tyrosine" is from the Greek tyros, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Cheese is a Food made from Milk, usually the milk of cows, Buffalo, Goats or sheep, by coagulation. Justus von Liebig ( May 12, 1803 &ndash April 18, 1873) was a German Chemist [2][3]

Contents

Functions

Aside from being a proteogenic amino acid, tyrosine has a special role by virtue of the phenol functionality. Phenol, is a toxic colourless Crystalline Solid with a sweet tarry odor commonly referred to as a "hospital smell" It occurs in proteins that are part of signal transduction processes. In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another It functions as a receiver of phosphate groups that are transferred by way of protein kinases (so-called receptor tyrosine kinases). A protein kinase is a Kinase Enzyme that modifies other Proteins by chemically adding Phosphate groups to them ( Phosphorylation) Receptor tyrosine kinases (RTKs are the high affinity Cell surface receptors for many polypeptide Growth factors Cytokines and Hormones Phosphorylation of the hydroxyl group changes the activity of the target protein.

A tyrosine residue also plays an important role in photosynthesis. Photosynthesis is a Metabolic pathway that converts Light Energy into Chemical energy. In chloroplasts (photosystem II), it acts as an electron donor in the reduction of oxidized chlorophyll. Chloroplasts are Organelles found in Plant cells and eukaryotic Algae that conduct Photosynthesis. Photosystem II is the first protein complex in Light Dependent Photosynthesis. Chlorophyll is a green Pigment found in most Plants Algae and Cyanobacteria. In this process, it undergoes deprotonation of its phenolic OH-group. Deprotonation is a Chemistry term that refers to the removal of a Proton ( Hydrogen Cation H+ from a Molecule, forming This radical is subsequently reduced in the photosystem II by the four core manganese cluster.

Biosynthesis

Plant biosynthesis of tyrosine from shikimic acid.
Plant biosynthesis of tyrosine from shikimic acid. Shikimic acid, more commonly known as its anionic form shikimate, is an important biochemical Intermediate in plants and microorganisms

In plants and most microorganisms, tyr is produced via prephenate, an intermediate on the shikimate pathway. Prephenic acid, more commonly known by its anionic form prephenate, is an intermediate in the biosynthesis of the aromatic Amino acids Phenylalanine Shikimic acid, more commonly known as its anionic form shikimate, is an important biochemical Intermediate in plants and microorganisms Prephenate is oxidatively decarboxylated with retention of the hydroxyl group to give p-hydroxyphenylpyruvate, which is transaminated using glutamate as the nitrogen source to give tyrosine and α-ketoglutarate. Oxidative decarboxylation reactions are Oxidation reactions in which a carboxylate group is removed forming Carbon dioxide. Hydroxyl in Chemistry stands for a molecule consisting of an Oxygen atom and a Hydrogen atom connected by a Covalent bond. There are two chemical reactions known as transamination (or aminotransfer Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its Alpha-ketoglutaric acid is one of two Ketone derivatives of Glutaric acid.

Mammals synthesize tyrosine from the essential amino acid phenylalanine (phe), which is derived from food. Mammals ( class Mammalia) are a class of Vertebrate Animals characterized by the presence of Sweat glands, including sweat glands Phe redirects here For the BitTorrent feature see PHE. For the constellation see Phoenix (constellation. The conversion of phe to tyr is catalyzed by the enzyme phenylalanine hydroxylase, a monooxygenase. Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Phenylalanine hydroxylase ( is an Enzyme which catalyses the reaction causing the addition of an Hydroxyl group to the end of the 6-carbon aromatic ring of 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.

Metabolism

Catecholamine hormones produced from tyrosine metabolism.
Catecholamine hormones produced from tyrosine metabolism. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body

Phosphorylation and sulfation

Some of the tyrosine residues can be tagged with a phosphate group (phosphorylated) by protein kinases. Phosphorylation is the addition of a Phosphate (PO4 group to a Protein molecule or a small molecule A protein kinase is a Kinase Enzyme that modifies other Proteins by chemically adding Phosphate groups to them ( Phosphorylation) (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. Antibodies (also known as immunoglobulins, abbreviated Ig) are Gamma globulin Proteins that are found in Blood or other Bodily Tyrosine residues may also be modified by the addition of a sulfate group, a process known as tyrosine sulfation. Tyrosine sulfation is a Posttranslational modification where a Sulfate group is added to a Tyrosine residue of a protein molecule [4] Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase (TPST). Tyrosine sulfation is a Posttranslational modification where a Sulfate group is added to a Tyrosine residue of a protein molecule Like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine.

Precursor to hormones

In the adrenal gland, tyrosine is converted to levodopa by the enzyme tyrosine hydroxylase (TH). In Mammals the adrenal glands (also known as suprarenal glands) are the triangle-shaped Endocrine glands that sit on top of the Kidneys their Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins Tyrosine hydroxylase or tyrosine 3-monooxygenase is the Enzyme responsible for catalyzing the conversion of the Amino acid L-tyrosine to TH is also the rate-limiting enzyme involved in the synthesis of the catecholamine hormones dopamine, norepinephrine (noradrenaline), and epinephrine. The rate-determining step (RDS is a Chemistry term for the slowest step in a Chemical reaction. Hormones (from Greek ὁρμή - "impetus" are chemicals released by cells that affect cells in other parts of the body Dopamine is a Hormone and Neurotransmitter occurring in a wide variety of animals including both vertebrates and invertebrates Norepinephrine ( INN) (abbreviated norepi or NE) or noradrenaline ( BAN) (abbreviated NA or NAd) is a

The thyroid hormones triiodothyronine (T3) and thyroxine (T4) in the colloid of the thyroid also are derived from tyrosine. The thyroid is one of the largest Endocrine glands in the body Triiodothyronine, C15[[hydrogen H12]] I3[[nitrogen N]] O4, also known as T3, is a Thyroid Thyroxine, or 353'5'-tetra­iodothyronine (often abbreviated as T4) a form of Thyroid hormones is the major Hormone secreted by the A colloid is a type of mechanical Mixture where one substance is dispersed evenly throughout another The thyroid is one of the largest Endocrine glands in the body

Precursor to alkaloids

In Papaver somniferum, the opium poppy, tyrosine is used to produce the alkaloid morphine. The opium poppy, Papaver somniferum, is the type of Poppy from which Opium and many refined opiates such as Morphine, Thebaine This article is about the chemical compounds alkaloids For the Pharmaceutical company in the Republic of Macedonia see Alkaloid (company. Medical uses Morphine can be used as an analgesic in hospital settings to relieve pain in Myocardial infarction pain in

Precursor to pigments

Tyrosine is also the precursor to the pigment melanin. Melanin is a class of compounds found in the Plant, Animal and Protista kingdoms, where it serves predominantly as a Pigment.

Degradation

The decomposition of tyrosine to acetoacetate and fumarate. Two dioxygenases are necessary for the decomposition path. The end products can then enter into the citric acid cycle.
The decomposition of tyrosine to acetoacetate and fumarate. Acetoacetic acid is the Organic compound with the formula CH3C(OCH2CO2H Fumaric acid is the Chemical compound with the formula HO2CCH=CHCO2H Two dioxygenases are necessary for the decomposition path. The end products can then enter into the citric acid cycle. The citric acid cycle, also known as the tricarboxylic acid cycle ( TCA cycle) or the Krebs cycle, (or rarely the Szent-Györgyi–Krebs cycle

The decomposition of L-tyrosine (syn. para-hydroxyphenylalanine) begins with an α-ketoglutarate dependent transamination through the tyrosine transaminase to para-hydroxyphenylpyruvate. There are two chemical reactions known as transamination (or aminotransfer Pyruvic acid (CH3COCO2H is an alpha-keto acid. The Carboxylate Anion of pyruvic acid is known as 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). Homogentisic acid is the common name for 25-dihydroxyphenylacetic acid 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 glutathione as a coenzyme. Glutathione ( GSH) is a Tripeptide. It contains an unusual Peptide linkage between the amine group of Cysteine and the Carboxyl Coenzymes are small organic non- Protein Molecules that carry chemical groups between Enzymes Coenzymes are sometimes referred to as cosubstrates Fumarylacetoacetate is finally split via fumarylacetoacetate-hydrolase through the addition of a water molecule.

Thereby fumarate (also a metabolite of the citric acid cycle) and acetoacetate (3-ketobutyroate) are liberated. Fumaric acid is the Chemical compound with the formula HO2CCH=CHCO2H Acetoacetic acid is the Organic compound with the formula CH3C(OCH2CO2H Acetoacetate is a ketone body, which is activated with succinyl-CoA, and thereafter it can be converted into acetyl-CoA which in turn can be oxidized by the citric acid cycle or be used for fatty acid synthesis. Ketone bodies are three water-soluble compounds that are produced as by-products when Fatty acids are broken down for energy in the Liver and Acetyl-CoA is an important molecule in metabolism used in many biochemical reactions The citric acid cycle, also known as the tricarboxylic acid cycle ( TCA cycle) or the Krebs cycle, (or rarely the Szent-Györgyi–Krebs cycle Fatty acids are formed by the action of Fatty acid synthases from Acetyl-CoA and Malonyl-CoA precursors

Ortho- and meta-tyrosine

Enzymatic oxidation of tyrosine by phenylalanine hydroxylase (top) and non-enyzmatic oxidation by hydroxyl free radicals (middle and bottom).
Enzymatic oxidation of tyrosine by phenylalanine hydroxylase (top) and non-enyzmatic oxidation by hydroxyl free radicals (middle and bottom). Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Phenylalanine hydroxylase ( is an Enzyme which catalyses the reaction causing the addition of an Hydroxyl group to the end of the 6-carbon aromatic ring of In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell

Three isomers of tyrosine are known. This article is about the chemical concept For "isomerism" of atomic nuclei see Nuclear isomer. 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. Arene substitution patterns are part of Organic chemistry IUPAC nomenclature and pinpoint the position of Substituents other than Hydrogen in The m-tyr and o-tyr isomers, which are rare, arise through non-enzymatic free-radical hydroxylation of phenylalanine under conditions of oxidative stress. In Chemistry, radicals (often referred to as free radicals) are atoms molecules or ions with Unpaired electrons on an otherwise Open shell Oxidative stress is caused by an imbalance between the production of reactive oxygen and a biological system's ability to readily detoxify the reactive intermediates or easily [5][6]

m-Tyrosine and analogues (rare in nature and therefore available synthetically) have shown application in Parkinson's Disease, Alzheimer's disease and arthritis [7]. Parkinson's disease (also known as Parkinson disease or PD) is a degenerative disorder of the Central nervous system that often impairs the sufferer's Alzheimer's disease ( AD) also called Alzheimer disease or simply Alzheimer's, is the most common form of Dementia. Arthritis (from Greek arthro-, joint + -itis, inflammation plural arthritides is a group of conditions involving damage to the Joints of the body

Medical use

Tyrosine is a starting material for neurotransmitters and increases plasma neurotransmitter levels (particularly dopamine and norepinephrine)[8] but has little if any effect on mood. See Chemical synapse for an introduction to concepts and terminology used in this article [9][10][11] 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,[12] prolonged work and sleep deprivation,[13][14] with reductions in stress hormone levels,[15] reductions in stress-induced weight loss seen in animal trials,[12] improvements in cognitive and physical performance[10][16][17] seen in human trials. Because tyrosine hydroxylase is the rate limiting enzyme, however, effects are less significant than those of l-dopa.

Tyrosine does not seem to have any significant effect on mood, cognitive or physical performance in normal circumstances. [18][19][20] A daily dosage supported in the literature is about 100 mg/kg for an adult. [21] 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. [18] Tyrosine may decrease the absorption of other amino acids in high or chronic doses. It decreases absorption of l-dopa.

See also

References

  1. ^ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature (1983). In organic Chemistry tyramine (4-hydroxy- Phenethylamine, para-tyramine p-tyramine is a Monoamine compound derived from the Alkaptonuria ( black urine disease or alcaptonuria) is a rare inherited genetic disorder of Tyrosine metabolism Tyrosinemia (or "Tyrosinaemia" is an error of Metabolism, usually inborn in which the body cannot effectively break down the Amino acid Tyrosine Albinism (from Latin albus, "white" see extended etymology) is a form of hypopigmentary Congenital disorder, Tyrosine sulfation is a Posttranslational modification where a Sulfate group is added to a Tyrosine residue of a protein molecule Betalains are a class of Red and Yellow Indole -derived pigments found in Plants of the Caryophyllales. Nomenclature and Symbolism for Amino Acids and Peptides. Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology. Retrieved on 2007-05-17. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 1521 - Edward Stafford 3rd Duke of Buckingham, is executed for Treason.
  2. ^ Tyrosine. The Columbia Electronic Encyclopedia, 6th ed. Infoplease. com — Columbia University Press (2007). Retrieved on 2008-04-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1303 - The University of Rome La Sapienza is instituted by Pope Boniface VIII.
  3. ^ Douglas Harper (2001). Tyrosine. Online Etymology Dictionary. Retrieved on 2008-04-20. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1303 - The University of Rome La Sapienza is instituted by Pope Boniface VIII.
  4. ^ Hoffhines AJ, Damoc E, Bridges KG, Leary JA, Moore KL (2006). "Detection and purification of tyrosine-sulfated proteins using a novel anti-sulfotyrosine monoclonal antibody". J. Biol. Chem. 281 (49): 37877–87. doi:10.1074/jbc.M609398200. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17046811.  
  5. ^ 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 (2005). "Urinary ortho-tyrosine excretion in diabetes mellitus and renal failure: evidence for hydroxyl radical production". Kidney Int. 68 (5): 2281–7. doi:10.1111/j.1523-1755.2005.00687.x. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16221230.  
  6. ^ Molnár GA, Nemes V, Biró Z, Ludány A, Wagner Z, Wittmann I (2005). "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". Free Radic. Res. 39 (12): 1359–66. doi:10.1080/10715760500307107. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 16298866.  
  7. ^ 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
  8. ^ Rasmussen DD, Ishizuka B, Quigley ME, Yen SS (1983). A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. "Effects of tyrosine and tryptophan ingestion on plasma catecholamine and 3,4-dihydroxyphenylacetic acid concentrations". J. Clin. Endocrinol. Metab. 57 (4): 760–3. PMID 6885965.  
  9. ^ Leathwood PD, Pollet P (1982). "Diet-induced mood changes in normal populations". Journal of psychiatric research 17 (2): 147–54. PMID 6764931.  
  10. ^ a b Deijen JB, Orlebeke JF (1994). "Effect of tyrosine on cognitive function and blood pressure under stress". Brain Res. Bull. 33 (3): 319–23. doi:10.1016/0361-9230(94)90200-3. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 8293316.  
  11. ^ Lieberman HR, Corkin S, Spring BJ, Wurtman RJ, Growdon JH (1985). "The effects of dietary neurotransmitter precursors on human behavior. ". Am J Clin Nutr. 42 (2): 366-370. PMID 4025206.  
  12. ^ a b Hao S, Avraham Y, Bonne O, Berry EM (2001). "Separation-induced body weight loss, impairment in alternation behavior, and autonomic tone: effects of tyrosine". Pharmacol. Biochem. Behav. 68 (2): 273–81. doi:10.1016/S0091-3057(00)00448-2. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 11267632.  
  13. ^ Magill RA, Waters WF, Bray GA, Volaufova J, Smith SR, Lieberman HR, McNevin N, Ryan DH (2003). "Effects of tyrosine, phentermine, caffeine D-amphetamine, and placebo on cognitive and motor performance deficits during sleep deprivation". Nutritional Neuroscience 6 (4): 237–46. PMID 12887140.  
  14. ^ Neri DF, Wiegmann D, Stanny RR, Shappell SA, McCardie A, McKay DL (1995). "The effects of tyrosine on cognitive performance during extended wakefulness". Aviation, space, and environmental medicine 66 (4): 313–9. PMID 7794222.  
  15. ^ Reinstein DK, Lehnert H, Wurtman RJ (1985). "Dietary tyrosine suppresses the rise in plasma corticosterone following acute stress in rats". Life Sci. 37 (23): 2157–63. doi:10.1016/0024-3205(85)90566-1. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 4068899.  
  16. ^ Deijen JB, Wientjes CJ, Vullinghs HF, Cloin PA, Langefeld JJ (1999). "Tyrosine improves cognitive performance and reduces blood pressure in cadets after one week of a combat training course". Brain Res. Bull. 48 (2): 203–9. doi:10.1016/S0361-9230(98)00163-4. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10230711.  
  17. ^ Mahoney CR, Castellani J, Kramer FM, Young A, Lieberman HR (2007). "Tyrosine supplementation mitigates working memory decrements during cold exposure". Physiology and Behavior IN PRESS: 575. doi:10.1016/j.physbeh.2007.05.003. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 17585971.  
  18. ^ a b Chinevere TD, Sawyer RD, Creer AR, Conlee RK, Parcell AC (2002). "Effects of L-tyrosine and carbohydrate ingestion on endurance exercise performance". J. Appl. Physiol. 93 (5): 1590–7. doi:10.1152/japplphysiol.00625.2001. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 12381742.  
  19. ^ Strüder HK, Hollmann W, Platen P, Donike M, Gotzmann A, Weber K (1998). "Influence of paroxetine, branched-chain amino acids and tyrosine on neuroendocrine system responses and fatigue in humans". Horm. Metab. Res. 30 (4): 188–94. PMID 9623632.  
  20. ^ Thomas JR, Lockwood PA, Singh A, Deuster PA (1999). "Tyrosine improves working memory in a multitasking environment". Pharmacol. Biochem. Behav. 64 (3): 495–500. doi:10.1016/S0091-3057(99)00094-5. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document. PMID 10548261.  
  21. ^ Gelenberg, A. J. , Wojcik, J. D. , Growdon, J. H. , Sved, A. F. , and Wurtman, R. J. . Tyrosine for the Treatment of Depression (PDF). Retrieved on 2008-03-25. 2008 ( MMVIII) is the current year in accordance with the Gregorian calendar, a Leap year that started on Tuesday of the Common Events 1199 - Richard I is wounded by a crossbow bolt while fighting France which leads to his death on April 6.

External links

Dictionary

tyrosine

-noun

  1. (biochemistry) A nonessential amino acid C9H11NO3 found in most animal proteins, especially casein.
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