Dick_Tracy said:
L-Arginine is an important one too.
L-arginine
is a protein amino acid present in the proteins of all life forms. It is classified as a semi-essential or conditionally essential amino acid. This means that under normal circumstances the body can synthesize sufficient L-arginine to meet physiological demands. There are, however, conditions where the body cannot. L-arginine is essential for young children and for those with certain rare genetic disorders in which synthesis of the amino acid is impaired. Some stress conditions that put an increased demand on the body for the synthesis of L-arginine include trauma (including surgical trauma), sepsis and burns. Under these conditions, L-arginine becomes essential, and it is then very important to ensure adequate dietary intake of the amino acid to meet the increased physiological demands created by these situations.
L-arginine, even when it is not an essential amino acid as defined above, is a vital one. In addition to participating in protein synthesis, it plays a number of other roles in the body. These include the detoxification of ammonia formed during the nitrogen catabolism of amino acids via the formation of urea. In addition, L-arginine is a precursor in the formation of nitric oxide, creatine, polyamines, L-glutamate, L-proline, agmatin (a possible neurotransmitter in the brain) and the arginine-containing tetrapeptide tuftsin, believed to be an immunomodulator. L-arginine is a glycogenic amino acid; it can be converted to D-glucose and glycogen if needed by the body or it can be catabolized to produce biological energy.
L-arginine, when administered in high doses, stimulates pituitary release of growth hormone and prolactin and pancreatic release of glucagon and insulin. Intravenous L-arginine may be used as an aid in the evaluation of problems with growth and stature that may be due to growth hormone deficiency. Intravenous arginine hydrochloride may be used as a fourth-line agent in the treatment of severe metabolic alkalosis. L-arginine is also used as an immunonutrient in enteral and parenteral nutrition to help improve the immune status in those suffering from sepsis, burns and trauma.
L-arginine is predominately synthesized in the kidney. It is a key intermediate in the Krebs-Henseleit urea cycle. L-ornithine and L-citrulline are precursors in the synthesis of L-arginine, and L-arginine is converted to urea and L-ornithine via the enzyme arginase. The portion of L-arginine that is not converted to urea enters the circulation, and is distributed to the various tissues and metabolized as discussed above. A much smaller amount of L-arginine is produced in the liver.
The typical dietary intake of L-arginine is 3.5 to 5 grams daily. Most dietary L-arginine comes from plant and animal proteins. Small amounts of free L-arginine are found in vegetable juices and fermented foods, such as miso and yogurt. Soy protein and other plant proteins are richer in L-arginine than are animal proteins, which are richer in lysine. It is thought that the possible hypocholesterolemic effect of soy protein is due, at least in part, to the higher L-arginine content in this protein.
L-arginine is a basic amino acid with the molecular formula C6H14N4O2 and with a molecular
weight of 174.20 daltons. It has 3 pKs: pK1=2.18, pK2=9.09 and pK3=13.2. Therefore, it carries a positive charge at physiological pH. The stereoisomer of L-arginine, D-arginine, does not have any biological activity, as far as we know. L-arginine is also known as 2-amino-5-guanidinovaleric acid and (S)-2-amino-5-[(aminoiminomethyl)amino] pentaenoic acid. Its one-letter abbreviation is R. It is also abbreviated as Arg. The terms L-arginine and arginine are frequently used interchangeably. The structural formula of L-arginine is as follows:
.