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threonine

 
Dictionary: thre·o·nine   (thrē'ə-nēn', -nĭn) pronunciation
 
n.

A colorless crystalline amino acid, C4H9NO3, that is obtained from the hydrolysis of protein and is an essential component of human nutrition.

[Probably from threose, a kind of sugar (alteration of erythrose : ERYTHRO– + –OSE2) + –INE2.]


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An essential amino acid. It was the last of the protein amino acids to be discovered, in 1935, in studies of nitrogen balance on subjects fed mixtures of the then known amino acids in place of proteins.

 
Food and Fitness: threonine
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An essential amino acid, but as it is found in all proteins, a specific deficiency is very unlikely. If taken as a single amino acid supplement, excessive doses of threonine may lead to an increase in urea production and possible toxicity.

 
Dental Dictionary: threonine
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(thrē′ōnīn)
n

One of the essential amino acids needed for proper growth in infants and maintenance of nitrogen balance in adults. See also amino acid.

 

One of the essential amino acids. It occurs in the proteins of egg, milk, gelatin, and other biological substances and may be synthesized or obtained by hydrolyzing casein. It is used in nutritional and biochemical research and as a dietary supplement.

For more information on threonine, visit Britannica.com.

 

An essential amino acid that is found in beans and other legumes, corn, and other grains.

 
Columbia Encyclopedia: threonine
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threonine (thrē'ənēn) , organic compound, one of the 22 α-amino acids commonly found in animal proteins. Only the L-stereoisomer appears in mammalian protein. It is one of several essential amino acids needed in the diet; human beings cannot synthesize it from simpler metabolites. Young adults need about 14 mg of this amino acid per day per kilogram (6 mg per lb) of body weight. Although threonine participates in many reactions in bacteria, including the biosynthesis of vitamin B12 and isoleucine, its metabolic role in higher animals, including man, remains obscure. It is known only as a constituent of proteins, and even in that form it is relatively unreactive. In spite of the fact that its side chain has a hydroxyl group similar to that of serine, there is no indication that it participates in the catalytic functions of any enzyme. Threonine was isolated from the protein fibrin in 1935 and synthesized in the same year.


 
Veterinary Dictionary: threonine
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Thr; a naturally occurring, hydroxy amino acid.

 
Wikipedia: Threonine
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L-Threonine
IUPAC name
Identifiers
CAS number [72-19-5]
PubChem 6288
EC number 200-774-1
SMILES
Properties
Molecular formula C4H9NO3
Molar mass 119.12 g mol−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, 100 kPa)

Infobox references

Threonine (abbreviated as Thr or T)[1] 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 and tyrosine, threonine is one of three proteinogenic amino acids bearing an alcohol group.

The threonine residue is susceptible to numerous posttranslational modifications. The hydroxy 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

Allo-threonine

With two chiral centers, threonine can exist in four possible stereoisomers, or two possible diastereomers of L-threonine. However, the name L-threonine is used for one single enantiomer, (2S,3R)-2-amino-3-hydroxybutanoic acid. The second diastereomer (2S,3S), which is rarely present in nature, is called L-allo-threonine.

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.[2] Enzymes involved in a typical biosynthesis of threonine include:

  1. aspartokinase
  2. α-aspartate semialdehyde dehydrogenase
  3. homoserine dehydrogenase
  4. homoserine kinase
  5. threonine synthase.
Threonine biosynthesis

Metabolism

Threonine is metabolized in two ways:

Sources

Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, and sesame seeds.[citation needed]

Racemic threonine can be prepared from crotonic acid by alpha-functionalization using mercury(II) acetate.[3]

References

  1. ^ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature. "Nomenclature and Symbolism for Amino Acids and Peptides". Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. http://www.chem.qmul.ac.uk/iupac/AminoAcid/. Retrieved on 2007-05-17. 
  2. ^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
  3. ^ Carter, H. E.; West, H. D. (1955). "dl-Threonine". Org. Synth.; Coll. Vol. 3: 813. 

See also

External links


 
 

 

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
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Food and Fitness. Food and Fitness: A Dictionary of Diet and Exercise. Copyright © 1997, 2003 by Oxford University Press. All rights reserved.  Read more
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Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.  Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Threonine" Read more