Valine

Valine
L-valine-skeletal.svg
L-valine-3D-sticks.png
IUPAC name (S)-2-amino-3-methyl-butanoic acid
Identifiers
CAS number 72-18-4
PubChem 1182
SMILES
 
Properties
Molecular formula C5H11NO2
Molar mass 117.15 g mol−1
Except where noted otherwise, data are given for
materials in their standard state
(at 25 °C, 100 kPa)
Infobox references

Valine (abbreviated as Val or V)[1] is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)2. L-Valine is one of 20 proteogenic amino acids. Its codons are GUU, GUC, GUA, and GUG. This essential amino acid is classified as nonpolar. 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 does not fold correctly.

Contents

Biosynthesis

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-ketovalerate undergoes reductive amination with glutamate. Enzymes involved in this biosynthesis include:[2]

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

Synthesis

Racemic valine can be synthesized by bromination of isovaleric acid followed by amination of the α-bromo derivative[3]

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

Dietary aspects

Nutritional sources of valine include cottage cheese, fish, poultry, peanuts, sesame seeds, and lentils.

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. Retrieved on 2007-05-17.
  2. ↑ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISNB 1-57259-153-6.
  3. ↑ Marvel, C. S. “d,l-Valine” Organic Syntheses, Collected Volume 3, p.848 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0848.pdf

External links

The 20 Common Amino Acids ("dp" = data page)
Branched-chain amino acids
Isoleucine (dp) | Leucine (dp) | Valine (dp)
Non Branch-chain
Alanine (dp) | Arginine (dp) | Asparagine (dp) | Aspartic acid (dp) | Cysteine (dp) | Glutamic acid (dp) | Glutamine (dp) | Glycine (dp) | Histidine (dp) | Lysine (dp) | Methionine (dp) | Phenylalanine (dp) | Proline (dp) | Serine (dp) | Threonine (dp) | Tryptophan (dp) | Tyrosine (dp)
Other classifications
Essential amino acids | Ketogenic amino acid | Glucogenic amino acid
Major families of biochemicals
Saccharides · Carbohydrates · Glycosides ·  · Amino acids · Peptides · Proteins · Glycoproteins ·  · Lipids · Terpenes · Steroids · Carotenoids
Alkaloids · Nucleobases · Nucleic acids ·  · Enzyme cofactors · Flavonoids · Polyketides · Tetrapyrroles
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