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(tī`rəsēn), organic compound, one of the 20 amino acidsamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
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 commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein. It is not essential to the human diet, since it can be synthesized in the body from phenylalaninephenylalanine
, organic compound, one of the 22 α-amino acids commonly found in animal proteins. Only the l-stereoisomer appears in mammalian protein.
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. When the enzyme that catalyzes the transformation of phenylalanine to tyrosine is not active because of a hereditary defect, the serious disease known as phenylketonuriaphenylketonuria
(PKU), inherited metabolic disorder caused by a deficiency in a specific enzyme (phenylalanine hydroxylase). The absence of this enzyme, a recessive trait, prevents the body from making use of phenylalanine, one of the amino acids in most protein-rich foods, and
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 (PKU) results. Other defects in tyrosine metabolism include the rare hereditary disorder known as alkaptonuria, characterized by discharge of a urine which darkens on standing exposed to air. Tyrosine is a precursor of the adrenal hormones epinephrineepinephrine
, hormone important to the body's metabolism, also known as adrenaline. Epinephrine, a catecholamine, together with norepinephrine, is secreted principally by the medulla of the adrenal gland.
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 and norepinephrinenorepinephrine
, a neurotransmitter in the catecholamine family that mediates chemical communication in the sympathetic nervous system, a branch of the autonomic nervous system.
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 as well as of the thyroid hormones, including thyroxinethyroxine
, substance secreted by the thyroid gland. The hormone thyroxine forms by combining the amino acid tyrosine with iodine. Complexed to a protein, it is stored in the follicle stems between thyroid cells.
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. Melaninmelanin
, water-insoluble polymer of various compounds derived from the amino acid tyrosine. It is one of two pigments found in human skin and hair and adds brown to skin color; the other pigment is carotene, which contributes yellow coloring.
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, the skin and hair pigment, is also derived from this amino acid. Tyrosine residues in enzymes have frequently been shown to be associated with active sites. Modification of these residues with various chemicals often results in a change in the specificity of the enzyme toward its substrates or even in total destruction of its activity. In 1846 tyrosine was obtained as a product of the degradation of the protein casein (from cheese). It was synthesized in the laboratory in 1883, and its structure was thus determined.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



[β-(para-hydroxyphenyl)alanine; oxyphenylaminopropionic acid], an amino acid. Tyrosine exists in the form of optically active D-and L-forms and the racemic DL-form. L-tyrosine is a constituent of many proteins and peptides, such as casein, fibroin, keratin, and insulin. It is readily isolated from protein hydrolysates because of its poor solubility in water. Phosphate esters of L-tyrosine are also components of proteins.

Tyrosine is a replaceable amino acid that is formed in animals and humans by the enzymic oxidation of phenylalanine. Disruption of this process gives rise to a serious hereditary disease, phenylpyruvic oligophrenia. The oxidation of tyrosine by the enzyme tyrosinase is an important intermediate reaction in the biosynthesis

of melanins, norepinephrine, and epinephrine in humans. The iodinated derivatives of tyrosine—thyroxine and triiodothyronine—are thyroid hormones.

Tyrosine performs an important function as a precursor in the biosynthesis of alkaloids, such as morphine, codeine, and papaverine. The enzymic oxidation of L-tyrosine is used to obtain the drug L-dopa. The breakdown of tyrosine in the body, in which ascorbic acid plays a role, results in the formation of fumarte and acetoacetic acids, which are incorporated into the Krebs cycle in the form of acetyl coenzyme A.


Meister, A. Biokhimiia aminokislot. Moscow, 1961. (Translated from English.)
Lehninger, A. Biokhimiia. Moscow, 1974. (Translated from English.)


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


C9H11NO3 A phenolic alpha amino acid found in many proteins; a precursor of the hormones epinephrine, norepinephrine, thyroxine, and triiodothyronine, and of the black pigment melanin.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
L-Tyrosine and L-dopa quickly decompose to some other metabolites such as dopamine and dopachrome.
Biosynthesis of Rap in different augments of L-tyrosine. L-tyrosine was added to fermentation medium in different supplements namely; 1, 2, 5, 7.5, 10, 15, 20 and 30 g/L.
as potent catalysts for biotransformation of L-tyrosine into L-DOPA, an anti-Parkinson's drug," Pharmaceutical Biology, vol.
A mixture of 40 [micro]L of 0.1 M PBS buffer (pH 6.8) and 100 [micro]L of L-tyrosine was designated as solution 3.
The construction of an IQA producing bacterial platform therefore requires the use of Ralstonia solanacearum tyrosinase (TYR; EC, monophenol, L-DOPA: oxygen oxidoreductase) to produce L-DOPA from L-tyrosine. TYR is a copper containing monophenol monooxygenase that catalyzes the oxidation of the 3'-position of the L-tyrosine phenol-ring (Fig.
Participants were given capsules that contained Acerola Cherry, Alfalfa Sprouts, B vitamins (food source), Bovine/ovine Hypothalamus, Bovine Parotid, Bovine Thymus, Collinsonia Root, Ginkgo Bark, Kelp, L-Tyrosine (fermented grain extract-gluten free), Passion Flower, and Rice Bran.
Surprisingly, our results from peptide mass fingerprinting and bioinformatic analysis (data not shown) demonstrated that this protein was PO, showing monooxygenase activity with L-tyrosine as substrate (Fig.
* L-Tyrosine: Involved with neurotransmitters; can cause surges in the neurotransmitters norepinephrine, epinephrine and dopamine.
To do its job, the thyroid needs iodine, L-tyrosine (an amino acid), and selenium (a mineral which helps the iodine and L-tyrosine combine to make thyroid hormone).
Tokyo, Japan, Sept 26, 2006 - (JCN) - Kyowa Hakko today announced that it has developed the world's first fermentation-based method for the commercial production of L-Tyrosine. The company plans to start full-scale production in 2007.
Homogenates were sedimented at 26,000 x g for 10 min to remove storage vesicles containing catecholamines, which interfere with TH activity, and assays were conducted with 100 [micro]L aliquots of the supernatant solution in a total volume of 550 [micro]L Each assay contained final concentrations of 910 [micro]M FeS[O.sub.4], 55 [micro]M unlabeled L-tyrosine (Sigma), 9.1 [micro]M pyridoxal phosphate (Sigma), 36 [micro]M [beta]-mercaptoethanol, and 180 [micro]M 2-amino-6,7-dimethyl-4-hydroxy5,6,7,8-tetrahydropteridine HCl (Sigma), all in a buffer of 180 mM sodium acetate and 1.8 mM sodium phosphate (pH 6.1).
Korea Research Institute of Bioscience and Biotechnology (Taejon-si, South Korea) has patented a novel obligately symbiotic thermophile Symbiobacterium toebii SC-1(Accession NO: KCTC 0685BP), and a thermostable L-tyrosine phenol-lyase and L-tryptophan indole-lyase produced by Symbiobacterium toebii SC-1.