Tyrosine

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Tyrosine
Skeletal formula of the L-isomer
of L-tyrosine
L-Tyrosin phys.svg

L-Tyrosine at physiological pH
Tyrosine-from-xtal-3D-bs-17.png
Tyrosine-from-xtal-3D-sf.png
Names
IUPAC name
(S)-Tyrosine
Other names
L-2-Amino-3-(4-hydroxyphenyl)propanoic acid
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard
 100.000.419 Edit this at Wikidata
IUPHAR/BPS
KEGG
UNII
  • InChI=1S/C9H11NO3/c10-8(9(12)13)5-6-1-3-7(11)4-2-6/h1-4,8,11H,5,10H2,(H,12,13)/t8-/m0/s1 checkY
    Key: OUYCCCASQSFEME-QMMMGPOBSA-N checkY
  • Key: OUYCCCASQSFEME-UHFFFAOYSA-N
  • Key: OUYCCCASQSFEME-MRVPVSSYSA-N
  • N[C@@H](Cc1ccc(O)cc1)C(O)=O
  • Zwitterion: [NH3+][C@@H](Cc1ccc(O)cc1)C([O-])=O
Properties
C9H11NO3
Molar mass 181.191 g·mol−1
.0453 g/100 mL
-105.3·10−6 cm3/mol
Hazards
NFPA 704 (fire diamond)
1
1
0
Supplementary data page
Tyrosine (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

L-Tyrosine or tyrosine (symbol Tyr or Y)

non-essential amino acid with a polar side group. The word "tyrosine" is from the Greek tyrós, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese.[3][4] It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic than phenylalanine.[5] It is encoded by the codons UAC and UAU in messenger RNA
.

Functions

Aside from being a proteinogenic amino acid, tyrosine has a special role by virtue of the phenol functionality. It occurs in proteins that are part of signal transduction processes and functions as a receiver of phosphate groups that are transferred by way of protein kinases. Phosphorylation of the hydroxyl group can change the activity of the target protein, or may form part of a signaling cascade via SH2 domain binding.

A tyrosine residue also plays an important role in photosynthesis. In chloroplasts (photosystem II), it acts as an electron donor in the reduction of oxidized chlorophyll. In this process, it loses the hydrogen atom of its phenolic OH-group. This radical is subsequently reduced in the photosystem II by the four core manganese clusters.

Dietary requirements and sources

The Dietary Reference Intake for tyrosine is usually estimated together with phenylalanine. It varies depending on an estimate method, however the ideal proportion of these two amino acids is considered to be 60:40 (phenylalanine:tyrosine) as a human body has such composition.[6] Tyrosine, which can also be synthesized in the body from phenylalanine, is found in many high-

bananas.[7] For example, the white of an egg has about 250 mg per egg,[8] while lean beef, lamb, pork, salmon, chicken, and turkey contain about 1 g per 3 ounces (85 g) portion.[8]

Biosynthesis

prephenate
.

In plants and most microorganisms, tyrosine is produced via

α-ketoglutarate
.

Mammals synthesize 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 a hydroxyl group to the end of the 6-carbon aromatic ring of phenylalanine, such that it becomes tyrosine.

Metabolism

Conversion of phenylalanine and tyrosine to its biologically important derivatives.

Phosphorylation and sulfation

Some of the tyrosine residues can be tagged (at the hydroxyl group) with a phosphate group (phosphorylated) by protein kinases. In its phosphorylated form, tyrosine is called 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.[9] Tyrosine sulfation is catalyzed by tyrosylprotein sulfotransferase (TPST). Like the phosphotyrosine antibodies mentioned above, antibodies have recently been described that specifically detect sulfotyrosine.[10]

Precursor to neurotransmitters and hormones

In dopaminergic cells in the

epinephrine
(adrenaline).

The

thyroxine (T4) in the colloid of the thyroid
are also derived from tyrosine.

Biosynthetic pathways for catecholamines and trace amines in the human brain[11][12][13]
The image above contains clickable links
Tyrosine is a precursor to trace amine compounds and the catecholamines.

Precursor to alkaloids

The latex of Papaver somniferum, the opium poppy, has been shown to convert tyrosine into the alkaloid morphine and the bio-synthetic pathway has been established from tyrosine to morphine by using Carbon-14 radio-labelled tyrosine to trace the in-vivo synthetic route.[14]

Precursor to natural phenols

p-coumaric acid
.

Precursor to pigments

Tyrosine is also the precursor to the pigment melanin.

Role in coenzyme Q10 synthesis

Tyrosine (or its precursor phenylalanine) is needed to synthesize the benzoquinone structure which forms part of coenzyme Q10.

Degradation

fumarate. Two dioxygenases are necessary for the decomposition path. The end products can then enter into the citric acid cycle
.

The decomposition of L-tyrosine (syn. para-hydroxyphenylalanine) begins with an α-ketoglutarate dependent

para-hydroxyphenylpyruvate
. 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

maleylacetoacetate
is created.

coenzyme. Fumarylacetoacetate is finally split by the enzyme fumarylacetoacetate hydrolase
through the addition of a water molecule.

Thereby

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
.

Phloretic acid is also a urinary metabolite of tyrosine in rats.[16]

Ortho- and meta-tyrosine

free radicals
(middle and bottom).

Three

free-radical hydroxylation of phenylalanine under conditions of oxidative stress.[17][18]

m-Tyrosine and analogues (rare in nature but available synthetically) have shown application in Parkinson's disease, Alzheimer's disease and arthritis.[19]

Medical use

Tyrosine is a precursor to neurotransmitters and increases plasma neurotransmitter levels (particularly dopamine and norepinephrine),[20] but has little if any effect on mood in normal subjects.[21][22][23] A number of studies have found tyrosine is useful during stress, cold, fatigue (in mice),[24][25] prolonged work and sleep deprivation,[26][27] with reductions in stress hormone levels,[28] reductions in stress-induced weight loss seen in animal trials,[25] and improvements in cognitive and physical performance[22][29][30] seen in human trials.

Tyrosine does not seem to have any significant effect on cognitive or physical performance in normal circumstances,[31][32] but does help sustain working memory better during multitasking.[33] A 2015 systematic review found that "tyrosine loading acutely counteracts decrements in working memory and information processing that are induced by demanding situational conditions such as extreme weather or cognitive load" and therefore "tyrosine may benefit healthy individuals exposed to demanding situational conditions".[34]

Interactions

It is unknown if

MAOIs interact with tyrosine.[35]

Industrial synthesis

L-tyrosine and its derivatives (

food additives. Two methods were formerly used to manufacture L-tyrosine. The first involves the extraction of the desired amino acid from protein hydrolysates using a chemical approach. The second utilizes enzymatic synthesis from phenolics, pyruvate, and ammonia through the use of tyrosine phenol-lyase.[36] Advances in genetic engineering and the advent of industrial fermentation have shifted the synthesis of L-tyrosine to the use of engineered strains of E. coli.[37][36]

See also

References

  1. ^
    doi:10.1063/1.1679537
    .
  2. ^ "Nomenclature and Symbolism for Amino Acids and Peptides". IUPAC-IUB Joint Commission on Biochemical Nomenclature. 1983. Archived from the original on 9 October 2008. Retrieved 5 March 2018.
  3. ^ "Tyrosine". The Columbia Electronic Encyclopedia, 6th ed. Infoplease.com — Columbia University Press. 2007. Retrieved 2008-04-20.
  4. ^ Harper D (2001). "Tyrosine". Online Etymology Dictionary. Retrieved 2008-04-20.
  5. ^ "Amino Acids - Tyrosine". www.biology.arizona.edu. Retrieved 2018-01-31.
  6. PMID 17513429
    .
  7. ^ "Tyrosine". University of Maryland Medical Center. Archived from the original on 2020-04-06. Retrieved 2011-03-17.
  8. ^ a b Top 10 Foods Highest in Tyrosine
  9. PMID 17046811
    .
  10. PMID 22406006
    .
  11. PMID 19948186
    .
  12. PMID 15860375
    .
  13. PMID 24374199
    .
  14. ISSN 0368-1769
    .
  15. doi:10.1177/2326409817744230
    .
  16. doi:10.1016/S0021-9258(19)76930-0
    .
  17. PMID 16221230
    .
  18. S2CID 31154432
    .
  19. doi:10.1021/op700093y
    .
  20. PMID 6885965
    .
  21. PMID 6764931
    .
  22. ^
    S2CID 33823121
    .
  23. PMID 4025206
    .
  24. S2CID 41813026
    .
  25. ^
    S2CID 46405659
    .
  26. S2CID 21300076
    .
  27. PMID 7794222
    .
  28. PMID 4068899
    .
  29. S2CID 27927524
    .
  30. S2CID 207372821
    .
  31. PMID 12381742
    .
  32. PMID 9623632
    .
  33. S2CID 24717770
    .
  34. S2CID 30331663
    .
  35. ^ "Tyrosine: Benefits, Side Effects and Dosage". Healthline. 1 February 2018.
  36. ^
    S2CID 23088822
    .
  37. doi:10.1016/j.procbio.2012.04.005
    .

External links