Dictionary:

arginine

  (är'jə-nēn')

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An amino acid, C₆H₁₄N₄O₂, obtained from the hydrolysis or digestion of plant and animal protein.

[German Arginin, possibly from Greek arginoeis, bright.]

A basic amino acid. Not a dietary essential for adult human beings, but infants may not be able to synthesize enough to meet the high demands of growth so some may be required in infant diets.

Arginine is an amino acid that forms creatine, an important constituent of muscles. It is non-essential in adults but may be essential in premature infants. Some people believe that, because arginine is essential for muscle growth in premature infants, it may be advantageous for athletes to take amino acid supplements containing arginine, but there is little evidence to support this belief. See also amino acid supplements.

One of the essential amino acids for infants and children. See also amino acid.

Description

Arginine is one of the amino acids produced in the human body by the digestion, or hydrolysis of proteins. Arginine can also be produced synthetically. Because it is produced in the body, it is referred to as "nonessential," meaning that no food or supplements are necessary for humans to ingest. Arginine compounds can be used in treating people with liver dysfunction due to its role in promoting liver regeneration.

General Use

In March 2000 in Newsweek magazine, Stephen Williams noted the newly discovered role arginine might play in treating people with chronic heart failure (CHF). The study, as reported in the Journal of the American College of Cardiology involved 40 patients who suffered from CHF. Rainer Hambrecht and colleagues from the University of Leipzig in Germany did the research by dividing the group into four sections. One group took 8 g of arginine daily for four weeks. A second took no supplement, but did daily forearm exercises. The third did both the exercises, and took the supplement daily. The fourth group was a control group and did nothing except taking their usual medication, as did the others. Because of the known fact that arginine is naturally converted into nitric oxide by the human body, the result of that chemical relaxing blood vessels was also known when the experiment began. The group that took the arginine alone showed an improvement in their blood-vessel dilation by four times, as did the group doing exercises alone. The third who did both, showed an increase six times better than the original blood-dilation factor. Promise in the future use of arginine in treating heart patients with this condition was indicated as researchers continued to perform further tests. According to an article by Liz Brown written in Better Nutrition in June 2000, also discussing the Leipzig study, "Numerous other studies have shown that arginine has a vadodilatory effect on people with high cholesterol levels, those with high blood pressure and others with compromised circulation associated with heart disease."

Other research in the use of arginine has indicated that arginine is crucial to the wound-healing process, particularly in the elderly for whom blood circulation is poor. Arginine is necessary for growth periods but not for body maintenance.

Benefits of the use of arginine as a supplement include:

• improves immune response to bacteria, viruses, and tumor cells.
• promotes wound healing by repairing tissues
• plays a crucial role in the regeneration of liver
• responsible for release of growth hormones
• promotes muscle growth
• improves cardiovascular functioning

Arginine is used as a supplement in the treatment of heart patients with arterial heart disease; as an intravenous supplement to patients with liver dysfunction; as a supplement for easing exercise-related pains due to the heart muscle not getting enough blood to circulate to the muscles in the calves. Supplements that combine arginine with other amino acids, such as ornithine and lysine, are purported to assist in muscle-building exercises by minimizing body fat and maximizing muscle tone. Results vary among those who have taken these supplements. Arginine is also present in "multi" amino acids capsules that are taken as a dietary supplement.

New information released in 2002 showed that treatment with arginine improved immune function in HIV patients and proved safe for these patients when used on a short-term patients. Other new research was finding that arginine supplements worked as an effective anticoagulant, but unlike aspirin and other anticoagulants, could prevent clotting without increasing stroke risk. New research also is showing arginine's effectivenss in fighting cancer and protecting and detoxifying the liver, improving male fertility, and promoting healing.

Preparations

Arginine supplements as an alternative medicine therapy are normally taken in either tablet or capsule form. In naturopathic treatment of liver dysfunction, the supplement would be added intravenously as a powder diluted in liquid. Discoveries reported in 2000 indicated that in the treatment of arterial heart disease, the ingestion of arginine tablets or capsules of 6–9 g a day are helpful in dilating blood vessels to ease circulation and prevent the buildup of cholesterol.

Precautions

Long-term effects of arginine supplements have not yet been determined. Consultation with a physician regarding individual needs is always advised. Individuals who attempt to treat their own heart ailments, or intend to guard against any potential difficulty, should seek advice of a physician. Arginine does not show any positive results in treatment of men with damaged valves or enlarged heart tissue.

Arginine has been suspected in the formation of cold sores. Some practitioners suggest that consuming foods high in arginine, such as nuts, grains, and chocolates, can promote cold sores. Reducing intake of foods high in arginine and increasing intake of lysine (another amino acid) can reduce or even eliminate the cold sore problem.

Side Effects

As previously noted, the use of supplemental arginine should be monitored for use with specific problems. Overdose could result in unforeseen complications, while regular use might or might not help ease everyday problems, such as relaxation of muscles not due to the specific heart ailment of arterial disease. People who should not take arginine supplements are those predisposed to herpes outbreaks; cancer patients, due to possible increase in cell replication of cancerous cells; those with low blood pressure; and individuals with certain liver or kidney problems. Those taking blood thinners are advised to seek medical advice before taking the supplement. Pregnant women are also cautioned against taking the supplements due to the unknown affect it could have on both mother and child.

Interactions

Long-term studies are ongoing. While no adverse reactions of ordinary supplements of 6–9 g a day have yet been documented, caution is urged. Because amino acids are not drugs, their use is not regulated by the U.S. Food and Drug Administration (FDA). One study in April 1999 in HealthInform: Essential Information on Alternative Health Care reported that nutritional supplements of arginine with omega-3 fatty acids for outpatients with HIV showed no particular benefits in immunity.

Resources

Periodicals

"Arginine Treatment man Improve Immune Function." AIDS Weekly (September 23, 2002):3.

Brown, Edwin W. "Troubled by Cold Sores?" Medical Update (March 1999).

Brown, Liz. "Arginine and Exercise." Better Nutrition (June 2000).

Chowienczyk, Phil and Jim Ritter. "Arginine: NO more than a simple amino acid?" The Lancet 27 (September 1997).

Gerard, James M. and Atchawee Luisiri. "A fatal overdose of arginine hydrochloride." Journal of Toxicology (November 1997).

Henderson, Charles W. "Suppression of Arginine Transport and Nitric Oxide Synthesis in Activated Macrophages by Cat 2 Antisense Oligonucleotides." Cancer Weekly Plus (28 December 1998).

Klotter, Jule. "Arginine and Heart Disease." Townsend Letter for Doctors and Patients (August-September 2002): 22.

Marandino, Cristin. "Taking Heart." Vegetarian Times (November 1999).

Pessarosa, A.; Dazzi, D.; Negro, C.; Cebigni, C.; Vescovi, P. P. "Effects of Alcohol Consumption and Accompanying Diet on Metabolic Response to Arginine in Chronic Alcoholics." Journal of Studies on Alcohol (September 1999).

"Prospective Study tests Nutritional Supplements enriched with Arginine and Omega–3 Fatty Acids." Health Inform: Essential Information on Alternative Health Care (April 1999).

Rodale Press. "Bypass This Snack." Men's Health (November 1999).

Rodale Press. "Is Being Henpecked Hereditary?" Men's Health (January 2000).

Thomas, Clayton, L., M.D., M.P.H., ed. "Hyperkalemia." Taber's Cyclopedic Medica Dictionary. Edition 13 Philadelphia: F. A. Davis Company, 1977.

Webb, Denise. "Ease Exercise–Related Pains with Arginine." Prevention December 1999.

Williams, Stephen. "Passing the Acid Test." Newsweek 27 March 2000.

Other

"Arginine." Mosby's Medical, Nursing & Allied Health Dictionary, Edition 5 1998. Available from

[Article by: Jane Spehar; Teresa G. Odle]

For more information on arginine, visit Britannica.com.

A basic amino acid occurring in proteins and essential for many species, particularly the cat.

• a. amidinase — see arginase.
• a. deaminase test — see arginine dihydrolase test (below).
• a. dihydrolase test — a test for the identification of bacteria, based on the conversion of l-arginine to putrescine. In a positive result, the alkaline product is indicated by bromocresol purple. Called also arginine deaminase test.
• a. esterase — an androgen-dependent enzyme derived from the prostate which occurs in high concentrations in seminal plasma.
• a. nutritional deficiency — results in elevated blood ammonia concentration. Cats are particularly sensitive and within hours of eating an arginine-free diet, severe neurological signs develop, leading to death. In other species, cataracts have been reported in dogs and feather abnormalities occur in chickens on deficient diets.
• a. vasopressin — a potent vasoconstrictor in mammals.
• a. vasotocin — the normal antidiuretic hormone in birds; released from the avian posterior pituitary.

Chemical structure of L-arginine
Arginine
Systematic (IUPAC) name
2-amino-5-(diaminomethylidene amino)pentanoic acid
Identifiers
CAS number	74-79-3
PubChem	6322
Chemical data
Formula	C6H14N4O2
Molar mass	174.2 g/mol
SMILES	N[C@@H](CCCNC(N)=N)C(O)=O
Complete data

Arginine (abbreviated as Arg or R)^[1] is an α-amino acid. The L-form is one of the 20 most common natural amino acids. Its codons are CGU, CGC, CGA and CGG. In mammals, arginine is classified as a semiessential or conditionally essential amino acid, depending on the developmental stage and health status of the individual. Infants are unable to effectively synthesize arginine, making it nutritionally essential for infants. Adults, however, are able to synthesize arginine in the urea cycle.

Arginine was first isolated from a lupin seedling extract in 1886 by the Swiss chemist Ernst Schulze.

Structure

Arginine can be to be a basic amino acid because the part of the side chain nearest to the backbone is long, carbon-containing and hydrophobic, whereas the end of the side chain is a complex guanidinium group. With a pK_a of 12.48, the guanidinium group is positively charged in neutral, acidic and even most basic environments. Because of the conjugation between the double bond and the nitrogen lone pairs, the positive charge is delocalized. This group is able to form multiple H-bonds.

Synthesis

Arginine is synthesized from citrulline by the sequential action of the cytosolic enzymes argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL). This is energetically costly, as the synthesis of each molecule of argininosuccinate requires hydrolysis of adenosine triphosphate (ATP) to adenosine monophosphate (AMP); i.e., two ATP equivalents.

Citrulline can be derived from multiple sources:

• from arginine via nitric oxide synthase (NOS);
• from ornithine via catabolism of proline or glutamine/glutamate;
• from asymmetric dimethylarginine (ADMA) via DDAH.

The pathways linking arginine, glutamine, and proline are bidirectional. Thus, the net utilization or production of these amino acids is highly dependent on cell type and developmental stage.

On a whole-body basis, synthesis of arginine occurs principally via the intestinal–renal axis, wherein epithelial cells of the small intestine, which produce citrulline primarily from glutamine and glutamate, collaborate with the proximal tubule cells of the kidney, which extract citrulline from the circulation and convert it to arginine, which is returned to the circulation. Consequently, impairment of small bowel or renal function can reduce endogenous arginine synthesis, thereby increasing the dietary requirement.

Synthesis of arginine from citrulline also occurs at a low level in many other cells, and cellular capacity for arginine synthesis can be markedly increased under circumstances that also induce iNOS. Thus, citrulline, a coproduct of the NOS-catalyzed reaction, can be recycled to arginine in a pathway known as the citrulline-NO or arginine-citrulline pathway. This is demonstrated by the fact that in many cell types, citrulline can substitute for arginine to some degree in supporting NO synthesis. However, recycling is not quantitative because citrulline accumulates along with nitrate and nitrite, the stable end-products of NO, in NO-producing cells.^[2]

Function

Arginine plays an important role in cell division, the healing of wounds, removing ammonia from the body, immune function, and the release of hormones. Arginine, taken in combination with proanthocyanidins^[3] or yohimbine^[4], has also been used as a treatment for erectile dysfunction.

In proteins

The geometry, charge distribution and ability to form multiple H-bonds make arginine ideal for binding negatively charged groups. For this reason arginine prefers to be on the outside of the proteins where it can interact with the polar environment. Incorporated in proteins, arginine can also be converted to citrulline by PAD enzymes. In addition, arginine can be methylated by protein methyltransferases.

As a precursor

Arginine is the immediate precursor of NO, urea, ornithine and agmatine; is necessary for the synthesis of creatine; and can also be used for the synthesis of polyamines (mainly through ornithine and to a lesser degree through agmatine), citrulline, and glutamate. For being a precursor of NO, (relaxes blood vessels), arginine is used in many conditions where vasodilation is required. The presence of asymmetric dimethylarginine (ADMA), a close relative, inhibits the nitric oxide reaction; therefore, ADMA is considered a marker for vascular disease, just as L-arginine is considered a sign of a healthy endothelium.

Implication in herpes simplex viral replication

Tissues culture studies have shown the suppression of viral replication when the lysine to arginine ratio in vitro favors lysine. The therapeutic consequence of this finding is unclear, but dietary arginine may affect the effectiveness of lysine supplementation.^[5]

Implication in contributing to risk of death from heart disease

A recent Johns Hopkins study testing the addition of L-arginine to standard postinfarction treatment has implicated L-arginine supplementation with an increased risk of death in patients recovering from heart attack.^[6] This study has been discussed in some detail in : "Reverse Heart Disease Now" by Stephen T Sinatra MD and James C Roberts MD, publ. Wiley 2006 ISBN 0-471-74704-1 at pp 111 -113.

Growth hormone

Arginine increases the production of growth hormone.^[7] Reports of its effects on male muscular development are not clearly proven.

Prolactin

Although there haven't been thorough studies, some sources claim that arginine helps release prolactin, an estrogenic compound which is associated with lactation, and like all estrogenic compounds may curb the secretion of testosterone^{[citation needed]}. Thus some bodybuilders stay away from pure arginine, intaking only amounts naturally found in protein.

Food sources

Arginine is found in chocolate, wheat germ and flour, buckwheat, granola, oatmeal, dairy products (cottage cheese, ricotta, nonfat dry milk, skim yogurt), beef (roasts, steaks), pork (bacon, ham), nuts (coconut, pecans, cashews, walnuts, almonds, Brazil nuts, hazel nuts, peanuts), seeds (pumpkin, sesame, sunflower), poultry (chicken and turkey light meat), wild game (pheasant, quail), seafood (halibut, lobster, salmon, shrimp, snails, tuna in water), chick peas, cooked soybeans^[8], and some energy drinks.

References

1. ^ IUPAC-IUBMB Joint Commission on Biochemical Nomenclature. Nomenclature and Symbolism for Amino Acids and Peptides. Recommendations on Organic & Biochemical Nomenclature, Symbols & Terminology etc. Retrieved on 2007-05-17.
2. ^ Enzymes of arginine metabolism J Nutr. 2004 Oct; 134(10 Suppl): 2743S-2747S; PMID 15465778 Free text
3. ^ Stanislavov, R. and Nikolova. 2003. Treatment of Erectile Dysfunction with Pycnogenol and L-arginine. Journal of Sex and Marital Therapy, 29(3): 207 – 213.
4. ^ Lebret, T., Hervéa, J. M., Gornyb, P., Worcelc, M. and Botto, H. 2002. Efficacy and Safety of a Novel Combination of L-Arginine Glutamate and Yohimbine Hydrochloride: A New Oral Therapy for Erectile Dysfunction. European Urology 41(6): 608-613.
5. ^ Griffith RS, Norins AL, Kagan C. (1978). "A multicentered study of lysine therapy in Herpes simplex infection". Dermatologica. 156 (5): 257-267. PubMed. 
6. ^ Arginine Therapy in Acute Myocardial Infarction JAMA. 2006 Jan; Vol.295
   1. 1: 58-64; PMID 16391217
   "wpext">Abstract
7. ^ Alba-Roth J, Müller O, Schopohl J, von Werder K (1988). "Arginine stimulates growth hormone secretion by suppressing endogenous somatostatin secretion". J Clin Endocrinol Metab 67 (6): 1186-9. PMID 2903866. 
8. ^ L-Arginine Supplements Nitric Oxide Scientific Studies Food Sources. Retrieved on 2007-02-20.

External links

• NIST Chemistry Webbook

Major families of biochemicals
Peptides | Amino acids | Nucleic acids | Carbohydrates | Lipids | Terpenes | Carotenoids | Tetrapyrroles | Enzyme cofactors | Steroids | Flavonoids | Alkaloids | Polyketides | Glycosides
Analogues of nucleic acids:	The 20 Common Amino Acids	Analogues of nucleic acids:
Alanine (dp) | Arginine (dp) | Asparagine (dp) | Aspartic acid (dp) | Cysteine (dp) | Glutamic acid (dp) | Glutamine (dp) | Glycine (dp) | Histidine (dp) | Isoleucine (dp) | Leucine (dp) | Lysine (dp) | Methionine (dp) | Phenylalanine (dp) | Proline (dp) | Serine (dp) | Threonine (dp) | Tryptophan (dp) | Tyrosine (dp) | Valine (dp)

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