Leucine
- 2-amino -4-methyl -pentan- 1- acid
- Abbreviations: Leu ( Three letter code)
- L ( single letter code )
- 61-90-5 (L- enantiomer)
- 328-38-1 (D - enantiomer)
- 328-39-2 (racemate )
V06
Shimmering white crystal flakes
Fixed
1.29 g · cm -3
293-295 ° C
- PKCOOH: 2.33
- PKNH2: 9.74
- Poorly in water ( 24 g · l-1 at 20 ° C)
- Insoluble in ethanol and diethyl ether
Template: Infobox chemical / molecular formula search available
Leucine, abbreviated as Leu or L, is a proteinogenic α -amino acid. For higher organisms L- leucine [ Synonyms: ( S)- leucine ] an essential amino acid, presumably for the energy balance in muscle tissue plays a central role. The mirror image (synonym: enantiomers) of L- leucine is the D -leucine [ Synonym: (R ) -leucine ]. The latter does not occur in proteins. Leucine crystallizes in white plates, hence also the name come forwards ( gr λευκός: white).
In this text, the physiology relate solely to the L- leucine [ Synonyms: ( S)- leucine ]. When it is mentioned in this article and in the scientific literature without any addition " leucine " is always meant L- leucine. Racemic DL -leucine [ Synonym: ( RS)- leucine ] and enantiomerically pure D -leucine [ Synonym: (R ) -leucine ] are synthetically accessible and only have little practical significance. The racemization of L- amino acids can be used for amino acid dating - are used - an age determination for fossil bone material.
L- leucine is encoded by the codons UUA, UUG, CUU, CUC, CUA and CUG.
Leucine belongs together with its constitutional isomers isoleucine, norleucine, and tert- leucine to the group of leucine.
Properties
- Residual Name: leucyl -
- Essential: yes
- Side chain: lipophilic
- Van der Waals volume: 124
- Hydrophobicity: 3.8
Leucine is present predominantly as the "inner salt " or zwitterion, whose formation can be explained by the fact that the proton of the carboxyl group migrates to the lone pair of the nitrogen atom of the amino group.
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 where the leucine has its lowest solubility in water. The isoelectric point is 5.98. Racemic leucine, which was subjected to a better understanding of the homochiral in the biosphere circularly polarized synchrotron radiation shows an enantiomeric excess of 2.6%.
Occurrence
Leucine - peptidic bound - part animal and vegetable protein. The following examples relate in each case to 100 g of the food, in addition, the percentage of leucine is specified on the total protein:
All of these foods contain almost exclusively chemically bound L- leucine as a protein component, but no free L- leucine.
History
L- leucine was 1819/1820 for the first time characterized as a protein component.
Functions
L- Leucine is important for maintaining and building muscle tissue. It supports protein synthesis in muscle and liver, inhibits the breakdown of muscle protein and supports healing processes. As L- isoleucine L-leucine can also serve as an energy supplier. The estimates of the daily requirement for healthy adults range, depending on the method used, from 10 to 50 mg of leucine per kilogram of body weight. A deficiency is caused either by insufficient dietary intake or deficiency of vitamin B6.
Use
L-leucine is adjacent glycine proteinogenic L-amino acids and other components of the medical infusion solutions.
In motor sport leucine is used as a dietary supplement for muscle building.