| Revision as of 20:14, 31 October 2005 editBorisTM (talk | contribs)Extended confirmed users2,806 editsNo edit summary← Previous edit | Revision as of 11:15, 2 November 2005 edit undoBorisTM (talk | contribs)Extended confirmed users2,806 edits a major grammar and spell edditing is neededNext edit → | ||
| Line 1: | Line 1: | ||
| <!-- Here is an info table; skip past it to edit the text. --> | <!-- Here is an info table; skip past it to edit the text. --> | ||
| {{NatOrganicBox_header | image= |
{{NatOrganicBox_header | image=Arginine_2.png | width=320px | name=Arginine }} | ||
| {{OrganicBox_name | 2-Amino-5-guanidino-pentanoic acid }} | {{OrganicBox_name | 2-Amino-5-guanidino-pentanoic acid }} | ||
| {{OrganicBox_synonyms | Argamine<br />Argivene<br />Detoxargin<br />Levargin<br />Minophagen A<br />R-Gene }} | {{OrganicBox_synonyms | Argamine<br />Argivene<br />Detoxargin<br />Levargin<br />Minophagen A<br />R-Gene }} | ||
| Line 23: | Line 23: | ||
| <!-- TEXT --> | <!-- TEXT --> | ||
| '''Arginine''' (Arg) is an α-]. The L-form is one of the 20 most common natural AAs. In mammals, Arg is classified as a semiessential or conditionally essential AA, depending on the developmental stage and health status of the individual. | |||
| '''Arginine''' is one of the 20 most common natural ]s. It has a ] side chain ]. In non-hepatic tissues, arginine can be biosynthesized by the ] cycle (or ]). Even so, arginine is often classed as one of the 10 ]s. This need, evidently, is restricted to children. | |||
| == |
==Structure== | ||
| Arg can be considered to be somewhat amphipathic AA as 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 ] group. With p''K''<sub>a</sub> > 12, the guanidinium group is positively charged in neutral and acidic 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 ]. | |||
| ==Synthesis== | |||
| Arginine plays an important role in cell division, the healing of wounds, removing ammonia from the body, immune function, and the release of hormones. It can be found in many foods such as meat, poultry, dairy products, and fish. The body also uses arginine to produce ], which relaxes blood vessels. For this reason, it has been used to treat cardiovascular disorders such as heart failure, intermittent claudication, impotence, female sexual dysfunction, and interstitial cystitis. | |||
| Arg is synthesized from citrulline by the sequential action of the cytosolic enzymes ] and ]. This is energetically costly, as the synthesis of each molecule of argininosuccinate requires hydrolysis of ] to ]; i.e., 2 ATP equivalents. Citrulline can be derived from multiple sources: Arg via ], ] via catabolism of ] or ]/], or ADMA via DDAH. It is important to note that the pathways linking Arg, Glu, and Pro are bidirectional. Thus, the net utilization or production of these AAs is highly dependent on cell type and developmental stage. On a whole-body basis, synthesis of Arg occurs principally via the intestinal–renal axis, wherein epithelial cells of the small intestine, which produce citrulline primarily from Gln and Glu, collaborate with the proximal tubule cells of the kidney, which extract citrulline from the circulation and convert it to Arg, which is returned to the circulation. Consequently, impairment of small bowel or renal function can reduce endogenous Arg synthesis, thereby increasing the dietary requirement. Synthesis of Arg from citrulline also occurs at a low level in many other cells, and cellular capacity for Arg synthesis can be markedly increased under circumstances that also induce ]. Thus, citrulline, a coproduct of the NOS-catalyzed reaction, can be recycled to Arg in a pathway known as the citrulline-NO or Arg-citrulline pathway. This is demonstrated by the fact that in many cell types citrulline can substitute for Arg 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. | |||
| ==Function== | |||
| Arginine can be ], yielding ]. Conversion by ] to ] also yields the vasoactive mediator ]. Hence, its use is considered in many conditions where ] is required. | |||
| Arginine plays an important role in cell division, the healing of wounds, removing ammonia from the body, immune function, and the release of hormones. | |||
| ===In proteins=== | |||
| ⚫ | Incorporated in proteins, |
||
| The geometry, charge distribution and ability to form multiple H-bonds make Arg ideal for binding negatively charged groups. For this reason Arg prefers to be on the outside of the proteins where it can interact with the polar environment. | |||
| ⚫ | Incorporated in proteins, Arg can also be converted to ] by PAD enzymes. In addition, Arg can be ] by protein methyltransferases. | ||
| ===As a precursor=== | |||
| == Biochemistry == | |||
| Arg is the immediate precursor of NO, urea, Orn and agmatine; is necessary for the synthesis of ]; and can be used for the synthesis of polyamines (mainly through Orn and to a lesser degree through agmatine), citrulline, and Glu. | |||
| For being a precursor of NO, (relaxes blood vessels), Arg is in many conditions where ] is required. | |||
| The guanidyl group at the end of the arginine side chain is positively charged in neutral and acidic environments. Because of the conjugation between the double bond and the nitrogen lone pairs, the positive charge is delocalized. Arginine is often used as an activating agent in biocatalysis, in situations where a large, soft positive charge is useful; compare this to ] which presents a small, hard positive charge. | |||
| ==Sources== | |||
| It can be found in any protein containing foods such as meat, poultry, dairy products, fish, etc. | |||
| == Reference == | == Reference == | ||
Revision as of 11:15, 2 November 2005
Template:NatOrganicBox header Template:OrganicBox name Template:OrganicBox synonyms Template:OrganicBox abbreviations Template:OrganicBox formula Template:NatOrganicBox section physicalprop Template:OrganicBox mass Template:OrganicBox density Template:OrganicBox melt point Template:OrganicBox boil point Template:NatOrganicBox section chemprop Template:OrganicBox isoelectric point Template:OrganicBox pka Template:OrganicBox hbond acceptor Template:OrganicBox hbond donor Template:OrganicBox tautomers Template:NatOrganicBox section miscellaneous Template:OrganicBox CAS Template:OrganicBox EINECS Template:OrganicBox PubCnem Template:NatOrganicBox footer
Arginine (Arg) is an α-AA. The L-form is one of the 20 most common natural AAs. In mammals, Arg is classified as a semiessential or conditionally essential AA, depending on the developmental stage and health status of the individual.
Structure
Arg can be considered to be somewhat amphipathic AA as 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 pKa > 12, the guanidinium group is positively charged in neutral and acidic 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
Arg is synthesized from citrulline by the sequential action of the cytosolic enzymes ASS and ASL. This is energetically costly, as the synthesis of each molecule of argininosuccinate requires hydrolysis of ATP to AMP; i.e., 2 ATP equivalents. Citrulline can be derived from multiple sources: Arg via NOS, Orn via catabolism of Pro or Gln/Glu, or ADMA via DDAH. It is important to note that the pathways linking Arg, Glu, and Pro are bidirectional. Thus, the net utilization or production of these AAs is highly dependent on cell type and developmental stage. On a whole-body basis, synthesis of Arg occurs principally via the intestinal–renal axis, wherein epithelial cells of the small intestine, which produce citrulline primarily from Gln and Glu, collaborate with the proximal tubule cells of the kidney, which extract citrulline from the circulation and convert it to Arg, which is returned to the circulation. Consequently, impairment of small bowel or renal function can reduce endogenous Arg synthesis, thereby increasing the dietary requirement. Synthesis of Arg from citrulline also occurs at a low level in many other cells, and cellular capacity for Arg synthesis can be markedly increased under circumstances that also induce iNOS. Thus, citrulline, a coproduct of the NOS-catalyzed reaction, can be recycled to Arg in a pathway known as the citrulline-NO or Arg-citrulline pathway. This is demonstrated by the fact that in many cell types citrulline can substitute for Arg 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. Morris SM Jr, 2004
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.
In proteins
The geometry, charge distribution and ability to form multiple H-bonds make Arg ideal for binding negatively charged groups. For this reason Arg prefers to be on the outside of the proteins where it can interact with the polar environment. Incorporated in proteins, Arg can also be converted to citrulline by PAD enzymes. In addition, Arg can be methylated by protein methyltransferases.
As a precursor
Arg is the immediate precursor of NO, urea, Orn and agmatine; is necessary for the synthesis of creatine; and can be used for the synthesis of polyamines (mainly through Orn and to a lesser degree through agmatine), citrulline, and Glu. For being a precursor of NO, (relaxes blood vessels), Arg is in many conditions where vasodilation is required.
Sources
It can be found in any protein containing foods such as meat, poultry, dairy products, fish, etc.
Reference
| Encoded (proteinogenic) amino acids | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| General topics |  | ||||||||||
| By properties |
| ||||||||||
.svg){kind=small} | This biochemistry article is a stub. You can help Misplaced Pages by expanding it. |