Valine

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Valine
ValinenotatpH7.4.png
Valine at 7.4 pH.png
Names
IUPAC name
Valine
Other names
2-amino-3-methylbutanoic acid
Identifiers
516-06-3 YesY
72-18-4 (L-isomer) YesY
640-68-6 (D-isomer) YesY
ChEBI CHEBI:57762 YesY
ChEMBL ChEMBL43068 YesY
ChemSpider 6050 YesY
DrugBank DB00161 YesY
EC Number 208-220-0
4794
Jmol interactive 3D Image
KEGG D00039 YesY
PubChem 1182
UNII 4CA13A832H YesY
Properties[2]
C5H11NO2
Molar mass 117.15 g·mol−1
Density 1.316 g/cm3
Melting point 298 °C (568 °F; 571 K) (decomposition)
soluble
Acidity (pKa) 2.32 (carboxyl), 9.62 (amino)[1]
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
YesY verify (what is YesYN ?)
Infobox references

Valine (abbreviated as Val or V)[1] encoded by the codons GUU, GUC, GUA, and GUG is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated -+NH3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated –COO- form under biological conditions), and a side chain isopropyl variable group, classifying it as a non-polar amino acid. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet. Human dietary sources are any proteinaceous foods such as meats, dairy products, soy products, beans and legumes.

Along with leucine and isoleucine, valine is a branched-chain amino acid. In sickle-cell disease, valine substitutes for the hydrophilic amino acid glutamic acid in β-globin. Because valine is hydrophobic, the hemoglobin is prone to abnormal aggregation.

History and etymology[edit]

Valine was first isolated from casein in 1901 by Emil Fischer.[3] The name valine comes from valeric acid, which in turn is named after the plant valerian due to the presence of the acid in the roots of the plant.[4][5]

Nomenclature[edit]

According to IUPAC, carbon atoms forming valine are numbered sequentially starting from 1 denoting the carboxyl carbon, whereas 4 and 4' denote the two terminal methyl carbons.[6]

Biosynthesis[edit]

Valine is an essential amino acid, hence it must be ingested, usually as a component of proteins. It is synthesized in plants via several steps starting from pyruvic acid. The initial part of the pathway also leads to leucine. The intermediate α-ketoisovalerate undergoes reductive amination with glutamate. Enzymes involved in this biosynthesis include:[7]

  1. Acetolactate synthase (also known as acetohydroxy acid synthase)
  2. Acetohydroxy acid isomeroreductase
  3. Dihydroxyacid dehydratase
  4. Valine aminotransferase

Synthesis[edit]

Racemic valine can be synthesized by bromination of isovaleric acid followed by amination of the α-bromo derivative[8]

HO2CCH2CH(CH3)2 + Br2 → HO2CCHBrCH(CH3)2 + HBr
HO2CCHBrCH(CH3)2 + 2 NH3 → HO2CCH(NH2)CH(CH3)2 + NH4Br

See also[edit]

References[edit]

  1. ^ Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
  2. ^ Weast, Robert C., ed. (1981). CRC Handbook of Chemistry and Physics (62nd ed.). Boca Raton, FL: CRC Press. p. C-569. ISBN 0-8493-0462-8. 
  3. ^ "valine". Encyclopaedia Britannica Online. Retrieved 2015-12-06. 
  4. ^ "valine". Merriam-Webster Online Dictionary. Retrieved 2015-12-06. 
  5. ^ "valeric acid". Merriam-Webster Online Dictionary. Retrieved 2015-12-06. 
  6. ^ Jones, J. H., ed. (1985). Amino Acids, Peptides and Proteins. Specialist Periodical Reports 16. London: Royal Society of Chemistry. p. 389. ISBN 978-0-85186-144-9. 
  7. ^ 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 .
  8. ^ Marvel, C. S. (1940). "dl-Valine". Org. Synth. 20: 106. ; Coll. Vol. 3, p. 848 .

External links[edit]