Valine

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Valine
L-valine-structure-numbered.svg L-valine-3D-balls.png
Identifiers
CAS number 516-06-3 YesY, 72-18-4 (L-isomer) YesY, 640-68-6 (D-isomer) YesY
PubChem 1182
ChemSpider 6050 YesY
UNII 4CA13A832H YesY
EC-number 208-220-0
DrugBank DB00161
KEGG D00039 YesY
ChEBI CHEBI:57762 YesY
ChEMBL CHEMBL43068 YesY
Jmol-3D images Image 1
Properties[2]
Molecular formula C5H11NO2
Molar mass 117.15 g mol−1
Density 1.316 g/cm3
Melting point 298 °C (568 °F; 571 K) (decomposition)
Solubility in water soluble
Acidity (pKa) 2.32 (carboxyl), 9.62 (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)
 YesY (verify) (what is: YesY/N?)
Infobox references

Valine (abbreviated as Val or V)[3] is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)2. L-Valine is one of 20 proteinogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar. 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. It is named after the plant valerian. In sickle-cell disease, valine substitutes for the hydrophilic amino acid glutamic acid in hemoglobin. Because valine is hydrophobic, the hemoglobin is prone to abnormal aggregation.

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.[4]

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:[5]

  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[6]

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

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. ^ "Nomenclature and symbolism for amino acids and peptides (IUPAC-IUB Recommendations 1983)", Pure Appl. Chem. 56 (5), 1984: 595–624, doi:10.1351/pac198456050595 .
  4. ^ 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. 
  5. ^ 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 .
  6. ^ Marvel, C. S. (1940), "dl-Valine", Org. Synth. 20: 106 ; Coll. Vol. 3: 848 .

See also[edit]

External links[edit]