valine n : an essential amino acid found in proteins; important for growth in children and nitrogen balance in adults

English

Noun

1. An essential amino acid C5H11NO2 found in most animal proteins.

Translations

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 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.

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:

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

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

External links

• Isoleucine and valine biosynthesis