Valine
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2008-06-14T09:04:21Z
Numbo3-bot
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robot Modifying: [[id:Valin]]
{{NatOrganicBox
| image= [[Image:L-valine-skeletal.svg|180px|Skeletal formula of valine]]<br>[[Image:L-valine-3D-sticks.png|160px|3D stick model of valine molecule]]
| name=(''S'')-2-amino-3-methyl-butanoic acid
| PubChem = 1182
| CAS = 72-18-4
| SMILES = CC(C)C(N)C(=O)O
| C=5 | H=11 | N=1 | O=2
| mass=117.15 g/mol
}}
'''Valine''' (abbreviated as '''Val''' or '''V''')<ref>{{cite web | author=IUPAC-IUBMB Joint Commission on Biochemical Nomenclature | title=Nomenclature and Symbolism for Amino Acids and Peptides | work=Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc | url=http://www.chem.qmul.ac.uk/iupac/AminoAcid/ | accessdate=2007-05-17}}</ref> is an α-[[amino acid]] with the [[chemical formula]] HO<sub>2</sub>CCH(NH<sub>2</sub>)CH(CH<sub>3</sub>)<sub>2</sub>. L-Valine is one of 20 proteogenic amino acids. Its [[codon]]s 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 acids|branched-chain amino acid]]. It is named after the plant [[Valerian (herb)|valerian]]. In [[sickle-cell disease]], valine substitutes for the [[hydrophilic]] [[amino acid]] [[glutamic acid]] in [[hemoglobin]]. Because valine is [[hydrophobic]], the hemoglobin does not [[Protein folding|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:<ref>Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISNB 1-57259-153-6.</ref>
# [[Acetolactate synthase]] (also known as acetohydroxy acid synthase)
# [[Acetohydroxy acid isomeroreductase]]
# [[Dihydroxyacid dehydratase]]
# [[Valine aminotransferase]]
==Synthesis==
Racemic valine can be synthesized by bromination of [[3-Methylbutanoic acid|isovaleric acid]] followed by amination of the α-bromo derivative<ref>Marvel, C. S. “d,l-Valine” Organic Syntheses, Collected Volume 3, p.848 (1955). http://www.orgsyn.org/orgsyn/pdfs/CV3P0848.pdf</ref>
:HO<sub>2</sub>CCH<sub>2</sub>CH(CH<sub>3</sub>)<sub>2</sub> + [[Bromine|Br<sub>2</sub>]] → HO<sub>2</sub>CCHBrCH(CH<sub>3</sub>)<sub>2</sub> + [[hydrogen bromide|HBr]]
:HO<sub>2</sub>CCHBrCH(CH<sub>3</sub>)<sub>2</sub> + 2 NH<sub>3</sub> → HO<sub>2</sub>CCH(NH<sub>2</sub>)CH(CH<sub>3</sub>)<sub>2</sub> + NH<sub>4</sub>Br
==Dietary aspects==
[[Nutrition]]al sources of valine include cottage cheese, fish, poultry, peanuts, sesame seeds, and lentils.
==References==
<references/>
==External links==
*[http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/AminoAcid/IleVal.html Isoleucine and valine biosynthesis]
{{AminoAcids}}
[[Category:Branched-chain amino acids]]
[[Category:Proteinogenic amino acids]]
[[Category:Glucogenic amino acids]]
[[Category:Essential amino acids]]
[[Category:Essential nutrients]]
{{biochem-stub}}
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