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Structural formula
Structure of L-alanine
Structural formula of L -alanine, the naturally occurring enantiomer
Surname Alanine
other names
Molecular formula C 3 H 7 NO 2
Brief description

colorless solid

External identifiers / databases
CAS number
  • 56-41-7 ( L -alanine)
  • 338-69-2 ( D -alanine)
  • 302-72-7 ( DL -alanine)
EC number 200-273-8
ECHA InfoCard 100,000,249
PubChem 5950
ChemSpider 5735
DrugBank DB00160
Wikidata Q218642
Drug information
ATC code


Molar mass 89,10 g · mol -1
Physical state



1.40 g cm −3

Melting point

297 ° C (decomposition)

pK s value
  • 2.35 (COOH)
  • 9.87 (NH 3 + )
  • readily soluble in water
    (166.5 g kg −1 at 25 ° C;
    217.9 g kg −1 at 50 ° C;
    285.1 g kg −1 at 75 ° C;
    373.0 g kg −1 at 100 ° C)
  • poorly soluble in ethanol * insoluble in diethyl ether
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 .

Alanine , abbreviated to Ala or A , is a non-essential α - amino acid .


Alanine is chiral , so it occurs in two mirror-image forms, whereby L -alanine is a proteinogenic amino acid which, according to IUPAC, is also referred to as ( S ) -2-aminopropanoic acid or ( S ) -alanine. D- alanine [synonym: ( R ) -alanine] is found as a building block of murein , the basic substance of bacterial cell walls. There is also the non-proteinogenic β-alanine .

Whenever "alanine" is mentioned in this text or in the scientific literature without any additional name ( prefix ), L -alanine is meant.

Enantiomers of alanine
Surname L -alanine D -alanine
other names ( S ) -alanine ( R ) -alanine
Structural formula Structure of L-alanine Structure of D-alanine
CAS number 56-41-7 338-69-2
302-72-7 (racemate)
EC number 200-273-8 206-418-1
206-126-4 (racemate)
ECHA info card 100,000,249 100.005.835
100.005.571 (racemate)
PubChem 5950 71080
602 (racemate)
DrugBank DB00160 DB01786
- (racemate)
Wikidata Q218642 Q27076975
Q27101911 (racemate)


L- alanine was first isolated from silk fibroin in 1888.

In addition to proline , alanine is one of the two amino acids that were first synthesized and not previously isolated from plant or animal material. Alanine was found by Adolph Strecker in 1850 when he actually wanted to synthesize lactic acid by reacting acetaldehyde with ammonia and hydrocyanic acid in the presence of hydrochloric acid , using the Strecker synthesis named after him. Strecker chose the name as a derivation of the term aldehyde , since he received the amino acid from the acetaldehyde mentioned. Alanine was first obtained from organic material in 1875 by Paul Schützenberger , when he split silk in an autoclave using barite and was able to identify a mixture of glycine and alanine. Of the amino acids involved in building the protein chain, L- alanine represents 29.7%.


The industrial production of L -alanine is based on L - aspartic acid by splitting off the β - carboxy group in a biotechnological process. Racemic alanine obtained by the Strecker synthesis can be acetylated at the amino group and is then subjected to a racemate resolution . Using L - aminoacylase, the acetyl group of L - N- acetylalanine is cleaved enantioselectively and L -alanine is formed , while D - N -acetylalanine is not hydrolyzed. The separation of L -alanine and D - N -acetylalanine is easy. If D -alanine is required , D - N -acetylalanine is hydrolyzed under acidic conditions, i. i.e., the acetyl group is split off. If there is no need for D -alanine is that obtained in the kinetic resolution is D - N -Acetylalanin by the action of acetic anhydride is racemized and recycled.

DL -Alanine can also be synthesized from 2-bromopropanoic acid, but this process is of no industrial importance.

In the metabolism, L -alanine is synthesized from the end product of glycolysis , pyruvate , through transamination . Bacteria obtain the D -alanine they need from L -alanine by means of the enzyme alanine racemase ( EC ).  


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

Alanine is usually present as an "inner salt" or zwitterion , the formation of which can be explained by the fact that the proton of the carboxy group migrates to the lone pair of electrons on the nitrogen atom of the amino group :

At a physiological pH of 7.4, a large proportion of the alanine molecules are present as zwitterions. The isoelectric point of alanine is pH 6.1 and alanine reaches its lowest solubility in water, since almost all alanine molecules are present as zwitterions. The solution has the lowest electrical conductivity at this point because zwitterions as a whole are uncharged.

Physiological functions

In reverse of this synthesis reaction, it can also be enzymatically broken down to pyruvate again (transamination). The carbon skeleton can be used again via pyruvate to build up glucose ( gluconeogenesis ) or completely broken down via the citric acid cycle to generate energy. The oxidative deamination of L -alanine to pyruvate and ammonia, catalyzed by the enzyme alanine dehydrogenase, represents a further degradation possibility; it exemplifies how part of the amino acid metabolism is linked to the carbohydrate metabolism .

L -alanine is a non-essential amino acid for humans, so it can be produced biosynthetically by the human metabolism.

Alanine occurs - alongside other amino acids such as B. leucine and glutamic acid - preferred in α-helices of proteins . These amino acids promote the formation of this secondary structural element and are therefore also referred to as helix formers .


L- alanine is a component of infusion solutions for parenteral nutrition and dietetics.

The two enantiomers of alanine, provided with a protective group , are often used for the synthesis of peptides and proteins . Furthermore, L - or D -alanine are also used as starting material in stereoselective synthesis .

Related links

See also

Web links

Wiktionary: Alanine  - explanations of meanings, word origins, synonyms, translations
Commons : Alanine  - Collection of pictures, videos and audio files

Individual evidence

  1. a b c d Entry on alanine in the GESTIS substance database of the IFA , accessed on December 19, 2019(JavaScript required) .
  2. a b c Entry on alanine. In: Römpp Online . Georg Thieme Verlag, accessed on May 29, 2014.
  3. ^ Hans Beyer , Wolfgang Walter : Textbook of Organic Chemistry , Hirzel Verlag, Stuttgart 1991, ISBN 3-7776-0485-2 , p. 822.
  4. Robert C. Weast (Ed.): CRC Handbook of Chemistry and Physics . 1. Student Edition. CRC Press, Boca Raton, Florida 1988, ISBN 0-8493-0740-6 , pp. C-706.
  5. a b P. Schützenberger, Investigations on the protein bodies, Chem Centralblatt, Vol. 285–286 (1876).
  6. ^ Biography of Adolph Strecker ( Memento from January 21, 2012 in the Internet Archive )
  7. Adolph Strecker: About the artificial formation of lactic acid and a new body that is homologous to Glycocoll. In: Annals of Chemistry and Pharmacy. 75, 1850, pp. 27-45, doi: 10.1002 / jlac.18500750103 .
  8. S. Hansen: The discovery of proteinogenic amino acids from 1805 in Paris to 1935 in Illinois. ( Memento from June 15, 2016 in the Internet Archive ) Berlin 2015.
  9. Hans-Dieter Jakubke, Hans Jeschkeit: Amino acids, peptides, proteins. Verlag Chemie, Weinheim 1982, ISBN 3-527-25892-2 , p. 19.
  10. Yoshiharu Izumi, Ichiro Chibata, Tamio Itoh: Production and Use of Amino Acids. In: Angewandte Chemie. 90 (1987) pp. 187-194; also in: Angewandte Chemie International Edition. in English, 17 (1978), pp. 176-183.
  11. ^ Hans-Ulrich Blaser, Elke Schmidt: Asymmetric Catalysis on Industrial Scale. 1st edition. 2003, ISBN 3-527-30631-5 , there article by Harald Gröger and Karlheinz Drauz on pp. 131–145.
  12. W. Hartmeier: Immobilized biocatalysts - on the way to the second generation. In: Natural Sciences. 72, (1985) pp. 310-314 and literature cited there.
  13. Hans Beyer , Wolfgang Walter : Textbook of organic chemistry. 20th edition. S. Hirzel Verlag, Stuttgart 1984, ISBN 3-7776-0406-2 .
  14. Berg, Tymozcko, Stryer: Biochemistry. 5th edition. Spectrum Academic Publishing House, Heidelberg / Berlin 2003, ISBN 3-8274-1303-6 .
  15. ^ S. Ebel, HJ Roth (Ed.): Lexicon of Pharmacy. Georg Thieme Verlag, 1987, ISBN 3-13-672201-9 , p. 17.
  16. Jesse Philip Greenstein, Milton Winitz: Chemistry of Amino Acids. Vols 1-3, John Wiley & Sons, 1961, ISBN 0-471-32637-2 .
  17. Hans-Dieter Jakubke, Hans Jeschkeit: Amino acids, peptides, proteins. Verlag Chemie, Weinheim 1982, ISBN 3-527-25892-2 .
  18. ^ Karlheinz Drauz, Axel Kleemann , Jürgen Martens: Induction of asymmetry by amino acids . In: Angewandte Chemie . tape 94 , no. 8 , 1982, pp. 590-613 , doi : 10.1002 / anie.19820940804 .
  19. Jürgen Martens : Asymmetric syntheses with amino acids . In: Topics in current chemistry . tape 125 . Springer, Berlin 1984, ISBN 978-3-540-13569-2 , pp. 165-246 , doi : 10.1007 / 3-540-13569-3_5 .
  20. ^ Gary M. Coppola, Garry M. Coppola, Asymmetric Synthesis: Construction of Chiral Molecules Using Amino Acids . 2nd Edition. John Wiley & Sons, 1987, ISBN 0-471-82874-2 .