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| 'Valine' | |
|---|---|
 Chemical structure of Valine  Chemical structure of | |
| Systematic name | (''S'')-2-amino-3-methyl-butanoic acid |
| Abbreviations | 'Val V' |
| Chemical formula | C5H11NO2 |
| Molecular mass | 117.15 g mol-1 |
| Melting point | 315 °C |
| Density | 1.230 g cm-3 |
| Isoelectric point | 5.96 |
| p''K''a | 2.27 9.52 |
| PubChem | 1182 |
| CAS number | [72-18-4] |
| EINECS number | 200-773-6 |
'Valine' is an α-amino acid with the chemical formula HO2CCH(NH2)CH(CH3)2. L-Valine is one of 20 proteogenic amino acids. Its three letter code is Val, its one letter code is V, and 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 |
| Synthesis |
| Dietary aspects |
| References |
| External links |
Biosynthesis
As an essential amino acid, valine is not synthesized in animals, 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
# acetohydroxy acid isomeroreductase
# dihydroxyacid dehydratase
# valine aminotransferase
Synthesis
Racemic valine can be synthesized by bromination of isovaleric acid followed by amination of the α-bromo derivative[2]
: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. Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISNB 1-57259-153-6.
2. Marvel, C. S. “d,l-Valine” Organic Syntheses, Collected Volume 3, p.848 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0848.pdf
External links
★ Isoleucine and valine biosynthesis
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