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Open Access Articles- Top Results for Threonine

Threonine

Threonine
Skeletal formula
Ball-and-stick model
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IUPAC name
Threonine
Other names
2-Amino-3-hydroxybutanoic acid
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80-68-2 7pxY
72-19-5 (L-isomer)
ChEBI CHEBI:57926 7pxY
ChEMBL ChEMBL291747 7pxY
ChemSpider 6051 7pxY
DrugBank DB00156 7pxY
EC number 201-300-6
Jmol-3D images Image
PubChem Template:Chembox PubChem/format
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C4H9NO3
Molar mass Lua error in Module:Math at line 495: attempt to index field 'ParserFunctions' (a nil value). g·mol−1
(H2O, g/dl) 10.6(30°),14.1(52°),19.0(61°)
Acidity (pKa) 2.63 (carboxyl), 10.43 (amino)[1]
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Thermodynamic
data

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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
 14pxY verify (what is10pxY/10pxN?)
Infobox references

Threonine (abbreviated as Thr or T)[2] is an α-amino acid with the chemical formula HO2CCH(NH2)CH(OH)CH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar. Together with serine, threonine is one of two proteinogenic amino acids bearing an alcohol group (tyrosine is not an alcohol but a phenol, since its hydroxyl group is bonded directly to an aromatic ring, giving it different acid/base and oxidative properties). It is also one of two common amino acids that bear a chiral side chain, along with isoleucine.

The threonine residue is susceptible to numerous posttranslational modifications. The hydroxyl side-chain can undergo O-linked glycosylation. In addition, threonine residues undergo phosphorylation through the action of a threonine kinase. In its phosphorylated form, it can be referred to as phosphothreonine.

It is a precursor of glycine, and can be used as a prodrug to reliably elevate brain glycine levels.

History

Threonine was discovered as the last of the 20 common proteinogenic amino acids in the 1930s by William Cumming Rose.

Stereoisomerism

120px 120px
L-Threonine (2S,3R) and D-Threonine (2R,3S)
120px 120px
L-allo-Threonine (2S,3S) and D-allo-Threonine (2R,3R)

Threonine is one of two proteinogenic amino acids with two chiral centers. Threonine can exist in four possible stereoisomers with the following configurations: (2S,3R), (2R,3S), (2S,3S) and (2R,3R). However, the name L-threonine is used for one single diastereomer, (2S,3R)-2-amino-3-hydroxybutanoic acid. The second stereoisomer (2S,3S), which is rarely present in nature, is called L-allo-threonine. The two stereoisomers (2R,3S)- and (2R,3R)-2-amino-3-hydroxybutanoic acid are only of minor importance.[citation needed]

Biosynthesis

As an essential amino acid, threonine is not synthesized in humans, hence we must ingest threonine in the form of threonine-containing proteins. In plants and microorganisms, threonine is synthesized from aspartic acid via α-aspartyl-semialdehyde and homoserine. Homoserine undergoes O-phosphorylation; this phosphate ester undergoes hydrolysis concomitant with relocation of the OH group.[3] Enzymes involved in a typical biosynthesis of threonine include:

  1. aspartokinase
  2. β-aspartate semialdehyde dehydrogenase
  3. homoserine dehydrogenase
  4. homoserine kinase
  5. threonine synthase.
File:Threonine biosynthesis.svg
Threonine biosynthesis

Metabolism

Threonine is metabolized in two ways:

Sources

Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, Black turtle bean[4] and Sesame seeds.[5]

Racemic threonine can be prepared from crotonic acid by alpha-functionalization using mercury(II) acetate.[6]

References

  1. ^ Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
  2. ^ "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)", Pure Appl. Chem. 56 (5), 1984: 595–624, doi:10.1351/pac198456050595 .
  3. ^ Lehninger, Albert L.; Nelson, David L.; Cox, Michael M. (2000), Principles of Biochemistry (3rd ed.), New York: W. H. Freeman, ISBN 1-57259-153-6 .
  4. ^ http://ndb.nal.usda.gov/ndb/foods/show/4632?fg=&man=&lfacet=&count=&max=&sort=&qlookup=&offset=&format=Full&new=
  5. ^ http://nutritiondata.self.com/
  6. ^ Carter, Herbert E.; West, Harold D. (1940). "dl-Threonine". Org. Synth. 20: 101. ; Coll. Vol. 3, p. 813 .

External links