Valine

• L-valine
• (S)- valine
• D-valine
• (R) -valine
• 2-amino- 3-methyl- butanoic acid
• 2- Aminoisovaleriansäure
• Abbreviations: Val ( Three letter code)
• V ( single letter code )

• 72-18-4 (L- enantiomer)
• 640-68-6 (D - enantiomer)
• 516-06-3 (DL- enantiomer )

V06

White solid

Fixed

1.23 g · cm -3

295-300 ° C

• PKCOOH: 2.29
• PKNH2: 9.72

• Moderately in water ( 85 g · l-1 at 20 ° C)
• Insoluble in diethyl ether, acetone and benzene

Template: Infobox chemical / molecular formula search available

Valine, abbreviated as Val or V, is in its natural L form an essential proteinogenic α - amino acid found in small quantities in all the major proteins. The material name is derived from the Latin validus for strong and healthy. Valine was first isolated in 1901 by Hermann Emil Fischer from casein, a milk protein. Structurally, valine derives by substitution of the α - hydrogen atom by an amino group (-NH2) of the isovaleric acid.

In this article, the information concerning the physiology alone L- valine [ Synonyms: ( S)- valine ]. If it is mentioned in this text and in the scientific literature without any addition " valine " is always meant L- valine. Racemic valine [ Synonyms: DL- valine and ( RS)- valine ] has an economic importance as an intermediate in the chemical industry. Enantiomerically pure D-valine [ Synonym: (R) -valine ] is usually prepared from DL- valine, and has practical importance in the production of cyclosporin. The racemization of L- amino acids can be used for amino acid dating - are used - an age determination for fossil bone material.

L- and L- norvaline isovaline are constitutional isomers.

In the alcoholic fermentation by yeast enzymes valine to isobutanol, a component of fusel oil, fermented ( amino acid fermentation). Late harvested grapes have a significantly higher amino acid content, and valine content.

Nutrition

Since the human body can not produce valine, it is dependent on the dietary intake. The following examples of the content of proteinogenic bound valine are each based on 100 g of food, in addition, the percentage is indicated at the total protein.

All of these foods contain almost exclusively chemically bound L- valine as a protein component, but no free L- valine.

The estimates of the daily requirement for healthy adults range, depending on the method used, 10 to 29 mg of valine per kilogram of body weight.

Biochemical importance

Valine is needed as a building block for protein synthesis, but is available in protein-rich foods or in the event of mobilization of endogenous protein reserves for energy production. For example, valine is used as the two other amino acids having a branched carbon chain, leucine and isoleucine, the diet of the muscle. This plays a role in prolonged exertion or in periods of starvation when the body has to use its own reserves. The degradation of valine provides propionyl - CoA, which contributes after conversion to succinyl -CoA to replenish the citric acid cycle.

Representation and extraction

In the Strecker synthesis is produced DL- valine. For the resolution of DL- valine is acylated on the nitrogen atom. The thus formed DL -N- acetylvaline is subjected to enzymatic resolution. The enzyme L- acetylase enantioselectively hydrolysed while the amide bond in the LN- acetylvaline to acetic acid and L-valine, while DN- acetylvaline is unchanged.

L- valine can also be produced by fermentation, a process of biotechnology, can be obtained directly. The starting materials are dependent on the bacterial cultures used. As needed Bacillus lactofermentum glucose, acetic acid and B. flavum Corneybacterium acetoacephilum ethanol as the source of the backbone carbon. In order to increase the yield and to suppress the formation of undesired products, there are usually specially bred (genetically manipulated or selected ) cultures.

Properties

Valine has a lipophilic side chain. The octanol - water partition coefficient is -2.26 (log KOW ). The isoelectric point is 5.96, the van der Waals volume of 105 valine is present predominantly as the "inner salt " or zwitterion, whose formation can be explained by the fact that the proton of the carboxyl group on the lone pair of nitrogen atom of the amino group migrates.

In an electric field, the zwitterion migrates not because it is not loaded as a whole. Strictly speaking, this is at the isoelectric point ( at a certain pH value) of the case, in which the valine, has its lowest solubility in water.

Use

Valine can increase as a precursor ( building block of a finished product molecule ), the yield of penicillin - forming cultures.

It is a component of energy drinks and infusion solutions for parenteral nutrition.

The starting material for the selective preparation of enantiomerically pure substances has ( S)- valine practical importance in chemistry.