Valine

The title of this article is ambiguous. Further meanings are listed under valine (disambiguation) .

Structural formula
Illustration of L -Valin, the naturally occurring isomer
General
Surname	Valine
other names	2-amino-3-methylbutanoic acid 2-aminoisovaleric acid Abbreviations: Val ( three letter code ) V (one letter code )
Molecular formula	C 5 H 11 NO 2
Brief description	white solid with a faint odor
External identifiers / databases
CAS number 72-18-4 ( L -enantiomer) 640-68-6 ( D -enantiomer) 516-06-3 ( DL enantiomer mixture ) EC number 200-773-6 ECHA InfoCard 100,000,703 PubChem 6287 ChemSpider 6050 DrugBank DB00161 Wikidata Q483752
Drug information
ATC code	V06
properties
Molar mass	117.15 g · mol -1
Physical state	firmly
density	1.23 g cm −3
Melting point	295-300 ° C
pK s value	pK COOH : 2.29 pK NH 3 + : 9.72
solubility	moderate in water (85 g l −1 at 20 ° C) insoluble in diethyl ether , acetone and benzene
safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Valine , abbreviated to Val or V , is in its natural L -form an essential proteinogenic α - amino acid , which occurs in small amounts in all important proteins . The name of the substance is derived from the Latin validus for strong and healthy. Valine was first isolated in 1901 by Emil Fischer from casein , a milk protein. Structurally, valine is derived from isovaleric acid by substituting the α- hydrogen atom with an amino group (-NH ₂ ) .

In alcoholic fermentation , yeast enzymes ferment valine to form isobutanol , a component of fusel oil ( amino acid fermentation ). Grapes harvested late have a significantly higher amino acid content, including valine.

Isomers

Valine has a stereocenter, so there are two enantiomers . Whenever "valine" is mentioned in this text and in the scientific literature without any addition, the naturally occurring L -Valin [synonym: ( S ) -Valin] is always meant. In this article, the information on physiology also applies to L- valine alone .

Isomers of valine
Surname	L -Valin	D -Valin
other names	( S ) -Valin	( R ) -Valin
Structural formula
CAS number	72-18-4	640-68-6
	516-06-3 (unspec.)
EC number	200-773-6	211-368-9
	208-220-0 (unspec.)
ECHA info card	100,000,703	100.010.336
	100.007.474 (unspec.)
PubChem	6287	71563
	1182 (unspec.)
DrugBank	DB00161	-
	- (unspec.)
Wikidata	Q483752	Q27103152
	Q27109943 (unspec.)

Racemic valine [synonyms: DL -Valin and ( RS ) -Valin] is of economic importance as an intermediate in the chemical industry. Enantiomerically pure D -Valin [Synonym: ( R ) -Valin] is mostly produced from DL -Valin and is of practical importance in the production of cyclosporine . The racemization of L- amino acids can be used for amino acid dating - an age determination for fossil bone material.

L - isovaline and L - norvaline are constitutional isomers .

Occurrence

Since the human organism cannot produce valine, it is dependent on it being supplied with food. The following examples for the content of proteinogenically bound valine each relate to 100 g of the foodstuff, and the percentage of total protein is also given.

Food	Total protein	Valine	proportion of
Beef, raw	21.26 g	1055 mg	5.0%
Chicken breast fillet, raw	23.09 g	1145 mg	5.0%
Salmon, raw	20.42 g	1107 mg	5.4%
Chicken egg	12.58 g	0 859 mg	6.8%
Cow's milk, 3.7% fat	0 3.28 g	0 220 mg	6.7%
Walnuts	15.23 g	0 753 mg	4.9%
Wholemeal wheat flour	13.70 g	0 618 mg	4.5%
Wholemeal corn flour	0 6.93 g	0 351 mg	5.1%
Rice, unpeeled	0 7.94 g	0 466 mg	5.9%
Peas, dried	24.55 g	1159 mg	4.7%
Spirulina, dried	60 g	2387 mg	4%
Chlorella, dried	59 g	3800 mg	6.4%

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

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

Biochemical significance

Valine is required as a building block for protein biosynthesis , but can also be used to generate energy in a protein-rich diet or in the case of mobilizing the body's own protein reserves. For example, like the other two amino acids with a branched carbon chain, leucine and isoleucine , valine is used to nourish the muscles . This plays a role during prolonged exertion or in phases of hunger , when the body has to fall back on its own reserves. The breakdown of valine provides propionyl-CoA , which after conversion to succinyl-CoA helps to replenish the citric acid cycle .

Presentation and extraction

The preparation of valine can be done by the Strecker synthesis . The starting product is isobutanal (isobutyraldehyde):

The Strecker synthesis produces DL- valine. For the resolution of the racemate, DL- valine is acetylated on the nitrogen atom. The DL - N -acetylvaline thus formed is subjected to an enzymatic resolution . The enzyme L -acetylase hydrolyzes enantioselectively the amide bond in L - N -acetylvaline to acetic acid and L- valine, while D - N -acetylvaline remains unchanged.

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

properties

Valine has a lipophilic side chain . The octanol-water partition coefficient is −2.26 (log K _OW ). The isoelectric point is 5.96, the van der Waals volume is 105. Valine is mainly present as an “inner salt” or zwitterion , the formation of which can be explained by the fact that the proton of the carboxy group is attached to the lone pair of electrons Nitrogen atom of the amino group migrates.

Zwitterions of L -Valin (left) and D -Valin (right)

The zwitterion does not migrate in the electric field because it is uncharged as a whole. Strictly speaking, this is the case at the isoelectric point (at a certain pH value), at which the valine also has its lowest solubility in water.

use

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

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

As a starting material for the targeted production of enantiomerically pure substances, ( S ) -valine is of practical importance in chemistry.

literature

• Hans-Dieter Jakubke and Hans Jeschkeit: Amino acids, peptides, proteins , Verlag Chemie, Weinheim 1982, ISBN 3-527-25892-2 .
• Jesse Philip Greenstein and Milton Winitz: Chemistry of Amino Acids , John Wiley & Sons, 1962, Volumes 1 to 3, ISBN 0-471-32637-2 .
• Yoshiharu Izumi, Ichiro Chibata and Tamio Itoh: Production and Utilization of Amino Acids , in: Angewandte Chemie International Edition in English 1978 , 17 , pp. 176-183. doi : 10.1002 / anie.197801761 .

Web links

Commons : Valine  - Collection of pictures, videos and audio files

Wiktionary: Valine  - explanations of meanings, word origins, synonyms, translations

Wikibooks: Biochemistry and Pathobiochemistry: Valine, Leucine and Isoleucine Metabolism  - Learning and Teaching Materials

Individual evidence

1. ↑ ^{a b c d} Data sheet Valine (PDF) from Merck , accessed on December 25, 2019.
2. ↑ Valine data sheet from Sigma-Aldrich , accessed on October 22, 2016 ( PDF ).
3. ^ ^{A b} Hans Beyer and Wolfgang Walter : Textbook of Organic Chemistry , S. Hirzel Verlag, Stuttgart 1991, ISBN 3-7776-0485-2 , p. 823.
4. ↑ ^{a b} entry on valine. In: Römpp Online . Georg Thieme Verlag, accessed on December 25, 2014.
5. ↑ Hans-Dieter Jakubke, Hans Jeschkeit: amino acids, peptides, proteins , Verlag Chemie, Weinheim, 62, 1982, ISBN 3-527-25892-2 .
6. ↑ nutrient database of the US Department of Agriculture , 21st edition.
7. ↑ AV Kurpad, MM Regan, T. Raj, JV Gnanou: Branched-chain amino acid requirements in healthy adult human subjects. In: J. Nutr. 136 (1 Suppl); Jan 2006: pp. 256S-263S; PMID 16365094 .
8. ↑ JM Berg, JL Tymoczko, L. Stryer: Biochemistry. 6th edition. Spectrum Academic Publishing House, Elsevier GmbH, Munich 2007; Pp. 697-698, 735, 746; ISBN 978-3-8274-1800-5 .
9. ↑ C. Hansch; A. Leo; D. Hoekman: Exploring QSAR. Hydrophobic, electronic and steric constants ACS Professional Reference Book, American Chemical Society, Washington DC, 1995; ISBN 978-0-8412-2991-4 .
10. ↑ PM Hardy: The Protein Amino Acids in GC Barrett (editor): Chemistry and Biochemistry of the Amino Acids , Chapman and Hall, 1985, ISBN 0-412-23410-6 , p. 9.
11. ↑ S. Ebel and HJ Roth (editors): Lexikon der Pharmazie , Georg Thieme Verlag, 1987, p. 668, ISBN 3-13-672201-9 .
12. ^ Karlheinz Drauz, Axel Kleemann and Jürgen Martens: Induction of Asymmetry by Amino Acids , in: Angewandte Chemie , 1982 , 94 , pp. 590–613; Angewandte Chemie International Edition English , 1982 , 21 , pp. 584-608.
13. ↑ Jürgen Martens : Asymmetric Syntheses with Amino Acids , in: Topics in Current Chemistry , 1984 , 125 , pp. 165-246.