Alanine
- L-( ) -alanine
- α -alanine
- L- α - amino propionic acid
- (S)- alanine
- (S )-2- aminopropanoic acid
- D-(- ) -alanine
- Abbreviations: Ala ( Three letter code)
- A ( single letter code )
- 56-41-7 (L- alanine)
- 338-69-2 (D - alanine)
- 302-72-7 (DL- alanine)
V06
Colorless to yellowish solid
Fixed
1.42 g · cm -3
295-297 ° C ( decomposition)
- 2.35 (COOH)
- 9.87 (NH2)
- 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)
- Sparingly soluble in ethanol
- Insoluble in diethyl ether
Template: Infobox chemical / molecular formula search available
Alanine, abbreviated as Ala or A is a non-essential α -amino acid. It is chiral, that occur in two mirror image forms, the L-alanine is a proteinogenic amino acid, which is referred to by IUPAC as well as (S )-2- aminopropanoic acid, or ( S)- alanine. D -alanine [ Synonym: (R ) -alanine ] is found as a component of the murein, the basic substance of bacterial cell walls. There are also the non-protein β -alanine.
If it is mentioned in this text or in the scientific literature " alanine " without further suffix (prefix ), L- alanine is meant.
History
The amino acid was synthesized and named in 1850 by Adolph Strecker first time; Strecker it chose the name as a derivative of the term aldehyde, since he established the amino acid from acetaldehyde via named after him Strecker synthesis. L- alanine was first characterized in 1888 by T. Weyl as a protein component of silk fibers, it contains 29.7 % of L- alanine.
Synthesis
The industrial production of L-alanine is prepared from L-aspartic acid β -carboxyl group by elimination of the means of biotechnological processes. Product obtained by Strecker synthesis of racemic alanine can be acetylated at the amino group and is then subjected to an optical resolution. In this case, the acetyl group eliminated enantioselectively of LN- acetylalanine using L -aminoacylase and there is L-alanine, while DN- acetylalanine is not hydrolyzed. The separation of L -alanine and DN- acetylalanine is simple. D-alanine is required, as DN- acetylalanine is hydrolyzed under acidic conditions, that is, the acetyl group is cleaved off. If there is no requirement for D- alanine is that obtained in the kinetic resolution DN- acetylalanine is racemized by the action of acetic anhydride and recycled.
DL -alanine can be synthesized from 2- bromopropanoic acid, but this method has no industrial importance.
In the metabolism of L-alanine is synthesized by transamination from the final product of glycolysis, pyruvate. Bacteria obtain needed D- alanine from L- alanine by the enzyme alanine racemase ( EC 5.1.1.1 ).
Properties
Alanine is usually present as " inner salt " or zwitterion, whose formation can be explained by the fact that the proton of the carboxyl group migrates to the free electron pair of the nitrogen atom of the amino group:
At physiological pH of 7.4, a large portion of the molecules is present as an alanine zwitterion. The isoelectric point of alanine at pH 6.1 and alanine reached its lowest solubility in water, as almost all alanine molecules exist as zwitterions. The solution has the lowest electric conductivity, at this point, as zwitterions are unloaded as a whole.
Physiological Functions
In a reversal of this synthesis reaction can be enzymatically degraded to pyruvate again ( transamination ). Thus, the carbon skeleton via pyruvate can be to build glucose ( gluconeogenesis ) used or degraded via the citric acid cycle completely for energy again. The oxidative deamination of L -alanine to pyruvate and ammonia catalyzed by the enzyme alanine dehydrogenase is a possibility of further reduction; makes example shows how a part of the amino acid metabolism is linked to the carbohydrate metabolism.
L- Alanine is one for the people of non- essential amino acid, so it can be biosynthetically produced by the human metabolism.
Alanine occurs - in addition to other amino acids such as leucine and glutamic acid - in α -helices of proteins preferably. These amino acids favor the formation of this secondary structure element and are therefore also referred to as helix formers.
Use
Element of infusion solutions for parenteral nutrition and dietetics from.
Starting material in chemical synthesis
The two enantiomers of alanine, are provided with a protective group commonly used for the synthesis of peptides and proteins. Furthermore, L- or D- alanine also be used in the stereoselective synthesis as starting material.