Description
Valine (abbreviated as Val or V) 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.
Chemical Properties
White or almost white, crystalline powder or colourless crystals, soluble in water, very slightly soluble in alcohol.
Definition
ChEBI: The L-enantiomer of valine.
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-ketoisovalerate undergoes reductive amination with glutamate. Enzymes involved in this biosynthesis include :
Acetolactate synthase
Acetohydroxy acid isomeroreductase
Dihydroxyacid dehydratase
Valine aminotransferase.
General Description
Valine is an essential amino acid, involved in the biosynthesis of glutamine and alanine. Valine being a branched-chain amino acid (BCAA), maintains a balance among the BCAAs. L-Valine serves as an energy fuel.
Biochem/physiol Actions
Valine is an essential amino acid, involved in the biosynthesis of glutamine and alanine. Valine being a branched-chain amino acid (BCAA) maintains a balance among the BCAAs. L-Valine serves as an energy fuel. Long term deficiency of L-Valine leads to growth failure, organ damage and loss of muscle mass.
Side effects
L-valine is a natural substance that is necessary for our health. As such, it generally does not have any side effects. However, taking large quantities of L-valine can cause fatigue, nausea, and a lack of muscle coordination.
Extremely high doses of L-valine can be dangerous. Excessive levels of L-valine can cause your body to produce excess ammonia which is toxic.
Extremely high levels of L-valine can cause your skin to tingle and can lead to hallucinations.
Synthesis
Racemic valine can be synthesized by bromination of isovaleric acid followed by amination of the α-bromo derivative
HO2CCH2CH(CH3)2 + Br2 → HO2CCHBrCH(CH3)2 + HBr
HO2CCHBrCH(CH3)2 + 2 NH3 → HO2CCH(NH2)CH(CH3)2 + NH4Br
.
Purification Methods
Crystallise L-valine from water by addition of EtOH. It sublimes at 178-188o/0.03mm with 99.3% recovery and unracemised [Gross & Gradsky J Am Chem Soc 77 1678 1955]. [Perrin J Chm Soc 3125 1958, Greenstein & Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 pp 2368-23771961, Beilstein 4 IV 2659.]
Nomenclature
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.
