Difference between revisions of "Arginine" - New World Encyclopedia
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− | '''Arginine''' | + | '''Arginine''' is an α-[[amino acid]] and the [[Optical isomerism|<small>L</small>-form]], the only form involved in protein synthesis, is one of the 20 most common natural amino acids in [[protein]]s. |
+ | |||
+ | In mammals, arginine is classified as a semiessential or conditionally essential amino acid, depending on the developmental stage and health status of the individual. [[Amino acid#essential amino acid|Essential amino acids]] are those that cannot be synthesized by an animal, or at a rate sufficient to meet its physiological needs, and which therefore must be obtained from the diet. Adult humans can synthesize arginine in sufficient quantities, via the [[urea cycle]]. However, infants are unable to effectively synthesize arginine, making it nutritionally essential for infants. Thus, arginine (like histidine) are sometimes classified as essential amino acids, though they are generally considered essential only in children, | ||
Arginine was first isolated from a [[lupin]] seedling extract in 1886 by the Swiss chemist Ernst Schulze. | Arginine was first isolated from a [[lupin]] seedling extract in 1886 by the Swiss chemist Ernst Schulze. | ||
+ | |||
+ | Arginine's three letter code is Arg and its one letter code is R (IUPAC-IUB 1983). | ||
==Structure== | ==Structure== | ||
+ | In [[biochemistry]], the term [[amino acid]] is frequently used to refer specifically to ''alpha amino acids'': those amino acids in which the amino and carboxylate groups are attached to the same [[carbon]], the so-called α–carbon (alpha carbon). The general structure of these alpha amino acids is: | ||
+ | |||
+ | ''R'' | ||
+ | | | ||
+ | H<sub>2</sub>N-C-COOH | ||
+ | | | ||
+ | H | ||
+ | where ''R'' represents a ''side chain'' specific to each amino acid. The exception to this basic structure is [[proline]], whose side chain cyclizes onto the backbone, forming a ring structure in which a secondary amino group replaces the primary amino group. | ||
+ | |||
+ | Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in [[protein]]s. They are called proteinogenic amino acids. As the name "proteinogenic" (literally, protein building) suggests, these amino acid are encoded by the standard genetic code and participate in the process of protein synthesis. | ||
+ | |||
+ | |||
+ | |||
Arginine can be considered 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 [[guanidine|guanidinium]] group. With a p''K''<sub>a</sub> of 12.48, the guanidinium group is positively charged in neutral, acidic and even most basic environments. Because of the [[Conjugated system|conjugation]] between the double bond and the nitrogen lone pairs, the positive charge is delocalized. This group is able to form multiple [[Hydrogen bond|H-bonds]]. | Arginine can be considered 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 [[guanidine|guanidinium]] group. With a p''K''<sub>a</sub> of 12.48, the guanidinium group is positively charged in neutral, acidic and even most basic environments. Because of the [[Conjugated system|conjugation]] between the double bond and the nitrogen lone pairs, the positive charge is delocalized. This group is able to form multiple [[Hydrogen bond|H-bonds]]. | ||
+ | |||
+ | Arginine Arg R 2-Amino-5-guanidinopentanoic | ||
+ | acid H2N-C(=NH)-NH-[CH2]3-CH(NH2)-COOH | ||
==Synthesis== | ==Synthesis== | ||
Line 62: | Line 82: | ||
==References== | ==References== | ||
<references /> | <references /> | ||
− | + | * International Union of Pure and Applied Chemistry and International Union of Biochemistry and Molecular Biology (IUPAC-IUB) Joint Commission on Biochemical Nomenclature. 1983. [http://www.chem.qmul.ac.uk/iupac/AminoAcid Nomenclature and symbolism for amino acids and peptides: Recommendations on organic & biochemical nomenclature, symbols & terminology]. ''IUPAC-IUB''. Retrieved June 14, 2007. | |
* Longe, J. L. (Ed.) 2005. ''The Gale Encyclopedia of Alternative Medicine. Detroit: Thomson/Gale. ISBN 0787693960. | * Longe, J. L. (Ed.) 2005. ''The Gale Encyclopedia of Alternative Medicine. Detroit: Thomson/Gale. ISBN 0787693960. | ||
Revision as of 17:59, 15 June 2007
![]() ![]() 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 |
Mol. weight | 174.2 |
SMILES | N[C@@H](CCCNC(N)=N)C(O)=O |
Complete data |
Arginine is an α-amino acid and the L-form, the only form involved in protein synthesis, is one of the 20 most common natural amino acids in proteins.
In mammals, arginine is classified as a semiessential or conditionally essential amino acid, depending on the developmental stage and health status of the individual. Essential amino acids are those that cannot be synthesized by an animal, or at a rate sufficient to meet its physiological needs, and which therefore must be obtained from the diet. Adult humans can synthesize arginine in sufficient quantities, via the urea cycle. However, infants are unable to effectively synthesize arginine, making it nutritionally essential for infants. Thus, arginine (like histidine) are sometimes classified as essential amino acids, though they are generally considered essential only in children,
Arginine was first isolated from a lupin seedling extract in 1886 by the Swiss chemist Ernst Schulze.
Arginine's three letter code is Arg and its one letter code is R (IUPAC-IUB 1983).
Structure
In biochemistry, the term amino acid is frequently used to refer specifically to alpha amino acids: those amino acids in which the amino and carboxylate groups are attached to the same carbon, the so-called α–carbon (alpha carbon). The general structure of these alpha amino acids is:
R | H2N-C-COOH | H
where R represents a side chain specific to each amino acid. The exception to this basic structure is proline, whose side chain cyclizes onto the backbone, forming a ring structure in which a secondary amino group replaces the primary amino group.
Most amino acids occur in two possible optical isomers, called D and L. The L amino acids represent the vast majority of amino acids found in proteins. They are called proteinogenic amino acids. As the name "proteinogenic" (literally, protein building) suggests, these amino acid are encoded by the standard genetic code and participate in the process of protein synthesis.
Arginine can be considered 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 pKa 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.
Arginine Arg R 2-Amino-5-guanidinopentanoic acid H2N-C(=NH)-NH-[CH2]3-CH(NH2)-COOH
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.[1]
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[2] or yohimbine[3], 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 not 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.[4]
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.[5] 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.[6] 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 (Canadian 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[7], and some energy drinks.
ReferencesISBN links support NWE through referral fees
- ↑ File:Free review.png Enzymes of arginine metabolism J Nutr. 2004 Oct; 134(10 Suppl): 2743S-2747S; PMID 15465778 Free text
- ↑ Stanislavov, R. and Nikolova. 2003. Treatment of Erectile Dysfunction with Pycnogenol and L-arginine. Journal of Sex and Marital Therapy, 29(3): 207 – 213.
- ↑ 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.
- ↑ Griffith RS, Norins AL, Kagan C. (1978). A multicentered study of lysine therapy in Herpes simplex infection. Dermatologica. 156 (5): 257-267. PubMed.
- ↑ Arginine Therapy in Acute Myocardial Infarction JAMA. 2006 Jan; Vol.295 #1: 58-64; PMID 16391217 Abstract
- ↑ 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.
- ↑ L-Arginine Supplements Nitric Oxide Scientific Studies Food Sources. Retrieved 2007-02-20.
- International Union of Pure and Applied Chemistry and International Union of Biochemistry and Molecular Biology (IUPAC-IUB) Joint Commission on Biochemical Nomenclature. 1983. Nomenclature and symbolism for amino acids and peptides: Recommendations on organic & biochemical nomenclature, symbols & terminology. IUPAC-IUB. Retrieved June 14, 2007.
- Longe, J. L. (Ed.) 2005. The Gale Encyclopedia of Alternative Medicine. Detroit: Thomson/Gale. ISBN 0787693960.
External links
Template:ChemicalSources
Major families of biochemicals | ||
Peptides | Amino acids | Nucleic acids | Carbohydrates | Nucleotide sugars | 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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