| Threonine |
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Other names
2-Amino-3-hydroxybutanoic acid
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| Identifiers |
| CAS number |
80-68-2 Y,
72-19-5 (L-isomer) |
| PubChem |
6288 |
| ChemSpider |
6051 Y |
| EC number |
201-300-6 |
| DrugBank |
DB00156 |
| ChEBI |
CHEBI:57926 Y |
| ChEMBL |
CHEMBL291747 Y |
| Jmol-3D images |
Image 1 |
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InChI=1S/C4H9NO3/c1-2(6)3(5)4(7)8/h2-3,6H,5H2,1H3,(H,7,8)/t2-,3+/m1/s1 Y
Key: AYFVYJQAPQTCCC-GBXIJSLDSA-N Y
InChI=1S/C4H9NO3/c1-2(6)3(5)4(7)8/h2-3,6H,5H2,1H3,(H,7,8)/t2-,3+/m1/s1
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| Properties |
| Molecular formula |
C4H9NO3 |
| Molar mass |
119.12 g mol−1 |
| Solubility in water |
(H2O, g/dl) 10.6(30°),14.1(52°),19.0(61°) |
| Acidity (pKa) |
2.63 (carboxyl), 10.43 (amino)[1] |
| Supplementary data page |
Structure and
properties |
n, εr, etc. |
Thermodynamic
data |
Phase behaviour
Solid, liquid, gas |
| Spectral data |
UV, IR, NMR, MS |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa) |
| Y (verify) (what is: Y/N?) |
| Infobox references |
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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.
Contents
- 1 History
- 2 Stereoisomerism
- 3 Biosynthesis
- 4 Metabolism
- 5 Sources
- 6 References
- 7 External links
History
Threonine was discovered as the last of the 20 common proteinogenic amino acids in the 1930s by William Cumming Rose.
Stereoisomerism
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L-Threonine (2S,3R) and D-Threonine (2R,3S)
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| 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:
- aspartokinase
- β-aspartate semialdehyde dehydrogenase
- homoserine dehydrogenase
- homoserine kinase
- threonine synthase.
Metabolism
Threonine is metabolized in two ways:
- It is converted to pyruvate via threonine dehydrogenase. An intermediate in this pathway can undergo thiolysis with CoA to produce acetyl-CoA and glycine.
- In humans, it is converted to α-ketobutyrate in a less common pathway via the enzyme serine dehydratase, and thereby enters the pathway leading to succinyl-CoA.
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
- ^ Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
- ^ "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)", Pure Appl. Chem. 56 (5), 1984: 595–624, doi:10.1351/pac198456050595 .
- ^ 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 .
- ^ http://ndb.nal.usda.gov/ndb/foods/show/4632?fg=&man=&lfacet=&count=&max=&sort=&qlookup=&offset=&format=Full&new=
- ^ http://nutritiondata.self.com/
- ^ Carter, Herbert E.; West, Harold D. (1940), "dl-Threonine", Org. Synth. 20: 101 ; Coll. Vol. 3: 813 .
External links
- Food Sources of Threonine
- Threonine biosynthesis
- CID 205
- CID 6288
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The 20 common amino acids
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| General topics |
- Protein
- Peptide
- Genetic code
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| By properties |
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Aliphatic
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- Branched-chain amino acids (Valine
- Isoleucine
- Leucine)
- Methionine
- Alanine
- Proline
- Glycine
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Aromatic
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- Phenylalanine
- Tyrosine
- Tryptophan
- Histidine
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Polar, uncharged
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- Asparagine
- Glutamine
- Serine
- Threonine
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Positive charge (pKa)
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- Lysine (≈10.8)
- Arginine (≈12.5)
- Histidine (≈6.1)
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Negative charge (pKa)
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- Aspartic acid (≈3.9)
- Glutamic acid (≈4.1)
- Cysteine (≈8.3)
- Tyrosine (≈10.1)
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| Other classifications |
- Essential amino acid
- Ketogenic amino acid
- Glucogenic amino acid
- Non-proteinogenic amino acid
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- Biochemical families: carbohydrates
- alcohols
- glycoproteins
- glycosides
- lipids
- eicosanoids
- fatty acids / intermediates
- glycerides
- phospholipids
- sphingolipids
- steroids
- nucleic acids
- constituents / intermediates
- proteins
- Amino acids / intermediates
- tetrapyrroles / intermediates
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Amino acid metabolism metabolic intermediates
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| K→acetyl-CoA |
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lysine→
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- Saccharopine
- Allysine
- α-Aminoadipic acid
- α-Aminoadipate
- Glutaryl-CoA
- Glutaconyl-CoA
- Crotonyl-CoA
- β-Hydroxybutyryl-CoA
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leucine→
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- α-Ketoisocaproic acid
- Isovaleryl-CoA
- 3-Methylcrotonyl-CoA
- 3-Methylglutaconyl-CoA
- HMG-CoA
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tryptophan→alanine→
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- N'-Formylkynurenine
- Kynurenine
- Anthranilic acid
- 3-Hydroxykynurenine
- 3-Hydroxyanthranilic acid
- 2-Amino-3-carboxymuconic semialdehyde
- 2-Aminomuconic semialdehyde
- 2-Aminomuconic acid
- Glutaryl-CoA
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| G |
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G→pyruvate→citrate
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glycine→serine→
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- glycine→creatine: Glycocyamine
- Phosphocreatine
- Creatinine
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G→glutamate→
α-ketoglutarate
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histidine→
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- Urocanic acid
- Imidazol-4-one-5-propionic acid
- Formiminoglutamic acid
- Glutamate-1-semialdehyde
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proline→
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- 1-Pyrroline-5-carboxylic acid
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arginine→
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- Ornithine
- Putrescine
- Agmatine
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other
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- cysteine+glutamate→glutathione: γ-Glutamylcysteine
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G→propionyl-CoA→
succinyl-CoA
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valine→
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- α-Ketoisovaleric acid
- Isobutyryl-CoA
- Methacrylyl-CoA
- 3-Hydroxyisobutyryl-CoA
- 3-Hydroxyisobutyric acid
- 2-Methyl-3-oxopropanoic acid
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isoleucine→
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- 2,3-Dihydroxy-3-methylpentanoic acid
- 2-Methylbutyryl-CoA
- Tiglyl-CoA
- 2-Methylacetoacetyl-CoA
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methionine→
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- generation of homocysteine: S-Adenosyl methionine
- S-Adenosyl-L-homocysteine
- Homocysteine
- conversion to cysteine: Cystathionine
- alpha-Ketobutyric acid+Cysteine
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threonine→
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propionyl-CoA→
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G→fumarate
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phenylalanine→tyrosine→
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- 4-Hydroxyphenylpyruvic acid
- Homogentisic acid
- 4-Maleylacetoacetic acid
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G→oxaloacetate
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| Other |
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mt, k, c/g/r/p/y/i, f/h/s/l/o/e, a/u, n, m
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k, cgrp/y/i, f/h/s/l/o/e, au, n, m, epon
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m (A16/C10), i (k, c/g/r/p/y/i, f/h/s/o/e, a/u, n, m)
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- Biochemical families: carbohydrates
- alcohols
- glycoproteins
- glycosides
- lipids
- eicosanoids
- fatty acids / intermediates
- glycerides
- phospholipids
- sphingolipids
- steroids
- nucleic acids
- constituents / intermediates
- proteins
- Amino acids / intermediates
- tetrapyrroles / intermediates
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