Arginine

• L-Arginine, Arg, R
• (S)- arginine
• α -amino- δ - guanidinvaleriansäure
• Abbreviations: Arg ( Three letter code)
• R ( single letter code )

• C6H14N4O2 (arginine )
• C6H14N4O2 • HCl (arginine · hydrochloride)
• C6H14N4O2 · HCl · H2O (arginine hydrochloride · · hydrate)

• 74-79-3 (L- arginine)
• 1119-34-2 (L- arginine · hydrochloride)
• 332360-01-7 (DL- arginine hydrochloride · · hydrate)
• 157-06-2 (D - arginine)

• V06
• B05XB01

White solid

• 228.68 g · mol -1 (arginine hydrochloride · · hydrate)

Fixed

0.7 g · cm -3

238 ° C

• COOH: 2.0
• NH2: 9.0
• Guanidine group: 12.1 (strong base )

Good in water ( 150 g · l-1 at 20 ° C)

Attention

5110 mg · kg -1 ( LD50, rat, oral)

Template: Infobox chemical / molecular formula search available

L-arginine, abbreviated Arg or R is a proteinogenic α -amino acid. For humans it is semi-essential. The name derives from the Latin word argentum ( silver) because the amino acid was first isolated as the silver salt. This amino acid has the highest mass fraction of nitrogen of all proteinogenic amino acids. In the three-letter code L- arginine is abbreviated as Arg and in single letter code as R.

If it is mentioned in this text or in the scientific literature " arginine " without further suffix (prefix ), L- arginine is meant.

Occurrence

L- arginine is widespread. The following examples provide an overview of arginine contents and refer respectively to 100 g of food, in addition, the percentage of bound arginine is indicated at the total protein.

All of these foods contain almost exclusively chemically bonded L- arginine as a protein component, however, no free L-arginine.

History

L- arginine was first won by SG Hedindurch hydrolytic cleavage of keratin.

Properties

Arginine is an α - amino acid with a guanidine functionality in the side chain. Together with L- lysine and L -histidine, L- arginine belongs to the group of " basic " amino acids or hexon bases. They have a basic group, a guanidino group here, the protonated ( positively charged) is always in the neutral range. Arginine is readily soluble in water and reacts ( by binding of protons) alkaline. The guanidine group is protonated in both the acidic and neutral, as well as weak basic medium and carries a positive charge which is delocalized between the amino groups. Proteins that contain L-arginine, are hydrophilic, this charge, thus water-soluble.

Arginine 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 guanidino moiety which is more basic than the α -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 given pH, here 11.2 ) of the case in which the arginine also has its lowest solubility in water.

Free L- arginine has a bitter taste.

Stereochemistry

In the proteins exclusively comes L -arginine [ Synonym: ( S)- arginine ] before peptidic bound. To enantiomer is the mirror image D-arginine [ Synonym: (R) -arginine ], which does not occur in proteins. Racemic arginine [ Synonyms: DL -arginine and ( RS)- arginine ] has little significance.

Biosynthesis

In the urea cycle arises L-arginine from carbamoyl phosphate, L- ornithine and L- aspartate.

Industrial manufacturing processes

For the production of L-arginine, there are two methods:

• " Extraction " of protein hydrolysates of gelatin, hair or feathers. Here, the protein hydrolyzate ( amino acid mixture ) is separated by crystallization and ion exchange chromatography, and so - isolated L- arginine - in addition to other proteinogenic amino acids.
• Fermentation.

The thus obtained L- arginine may possibly be converted by reaction with hydrochloric acid into the more stable L- arginine · hydrochloride in an additional production step.

Functions

L- arginine is a source of high-energy nitrogen - phosphate compounds in organisms and is involved in numerous biological functions. It is used in seedlings and memory cells as a nitrogen reservoir. L-Arginine is a metabolite of the Urea Cycle, in which the ammonia (e.g., amino acids ) is formed in the degradation of nitrogen compounds, is converted into urea. L-Arginine is the sole precursor of nitric oxide ( NO), one of the smallest chemical messengers in the human body. With nitric oxide (NO ) synthase from L-arginine is produced the endothelium - derived relaxing factor ( EDRF ), which has been identified as NO. EDRF physiologically leads to vasodilation by the NO diffuses into the muscle layer of the vessels. It activates soluble guanylate cyclase there and thus leads to relaxation of smooth muscle and relaxation of vascular tone. Studies show that arginine can significantly lower high blood pressure over this vasodilatation.

Due to the vasodilator function finds arginine in bodybuilding as a so-called "pump - Supplement " application without this biological effect is proved. Furthermore, the NO, resulting in inhibition of platelet aggregation and adhesion. Thus, the willingness of thrombotic changes in vascular plaque rupture is reduced, the most common cause of cerebral insults. It is believed that arginine can affect the suppressed immune response in serious injury, nutritional deficiency, sepsis and postoperative positive. For additional administration improved cellular immune response, a decrease by Injury dysfunction of T cells and increased phagocytosis is observed. In addition, the formation of endothelial dysfunction ( impaired vascular function ) is prevented.

In 1998, the scientists Robert F. Furchgott, Louis J. Ignarro and Ferid Murad for the exploration of the relationship between arginine and NO the Nobel Prize for Medicine.

Demand

Humans can synthesize arginine within the urea cycle itself, but the resulting sets are not sufficient to fully meet the demand, especially in adolescent people. Therefore, L-arginine is essential for children. But even in adults, the need for L- arginine by the body's own production is often not adequately covered. Especially in the growth phase, due to stress, in various diseases (eg atherosclerosis, hypertension, erectile dysfunction, vascular disease ) or after accidents, the need for arginine exceeds the amount produced by the human body. In old age, the demand for L-arginine increases greatly, since the endogenous counterpart, asymmetric dimethylarginine (ADMA ) is increased by a factor of 4, and therefore a 40-fold higher concentrations of arginine to neutralize the hazardous effects of this mortality factor are required. These quantities can be met only by dietary intake. Crucial to the need for L -arginine are therefore factors such as oxidative and nitrosative stress and ADMA level and thus the L-arginine - ADMA ratio.

At a protein intake of about 70-90 g / day results in a calculated daily arginine intake of about 1-5 g / day.

Medical use

L- arginine is used for the treatment of severe metabolic alkalosis. In pediatrics L -arginine is also indicated for the treatment of arising in a severe inborn error of metabolism increased ammonia content in the blood ( hyperammonemia ). Diagnosis L -arginine is used for evaluation of a growth hormone deficiency in dwarfism.

As a ( semi) -essential amino acid L -arginine is an obligatory component of parenteral nutrition. In electrolyte concentrates for addition to infusion solutions and in oral dietetics L -arginine is also used.

Used pharmaceutically usually the L-arginine hydrochloride.

Supplements

Arginine supplementation for the case of insufficient supply or increased demand as a dietetic food, especially as a food for special medical purposes, marketed under dietary regulation in various disease states such as erectile dysfunction, atherosclerosis at an early stage, endothelial dysfunction and hypertension. These indications are established for the dietary management of patients. The use of health claims ( health claims ), which, however, the contribution of L- arginine on healthy people to support the circulatory system ( maintenance of normal blood circulation, healthy blood pressure and hematopoiesis ), to support and improve the erection and to strengthen the muscles and relate to the provision of nitric oxide in the metabolism, the European food Safety authority (EFSA ) assessed so far not justified scientifically. This assessment was based on now-obsolete data in healthy volunteers. Recent original papers and meta- analyzes and systematic reviews now occupy the health-promoting effects of L- arginine in healthy subjects as well as in atherosclerosis, endothelial dysfunction and hypertension and recommend dietary amino acid as the treatment of cardiovascular diseases underlying metabolic disorders.