Arginine, also known as l-arginine.



It is an α-amino acid that is used in the biosynthesis of proteins.



Arginine contains an α-amino group, an α-carboxylic acid group, and a side chain consisting of a 3-carbon aliphatic straight chain ending in a guanidino group. 



It is the precursor for the biosynthesis of nitric oxide. 



It is encoded by the codons CGU, CGC, CGA, CGG, AGA, and AGG.



Preterm infants are unable to synthesize or create arginine: arginine  is amino acid nutritionally essential for them.



Most healthy people do not need to supplement with arginine.



Argininine  is a component of all protein-containing foodsand can be synthesized in the body from glutamine via citrulline.



It is obtained by hydrolysis of protein, such as gelatin.



It is obtained commercially by fermentation. 



Arginine is a conditionally essential amino acid in humans, as it may be required depending on the health status or lifecycle of the individual. 



Immature and rapidly growing individuals require additional arginine in their diet.



Additional dietary arginine is necessary for healthy individuals under physiological stress: recovery from burns, injury and sepsis.



Additional dietary arginine is necessary 


if the major sites of arginine biosynthesis, the small intestine and kidneys, have reduced function.



Animal sources of arginine include meat, dairy products, and eggs.



Plant sources include seeds of all types: grains, beans, and nuts.



Arginine is synthesized from citrulline by the sequential action of the cytosolic enzymes argininosuccinate synthetase and argininosuccinate lyase. 



Citrulline is derived from multiple sources:



from arginine itself via nitric oxide synthase 



as a byproduct of the production of nitric oxide for signaling purposes



from ornithine through the breakdown of proline or glutamine/glutamate



The pathways that link arginine, glutamine, and proline are bidirectional. 



Synthesis of arginine occurs principally via the intestinal–renal axis.



The epithelial cells of the small intestine produce citrulline, primarily from glutamine and glutamate, which is carried in the bloodstream to the proximal tubule cells of the kidney, which extract citrulline from the circulation and convert it to arginine, which is returned to the circulation. 



Impairment in  small bowel or renal function can therefore reduce arginine synthesis, increasing the dietary requirement.



Citrulline, a byproduct of the catalyzed production of nitric oxide, can be recycled to arginine.



Arginine’s roles include: cell division, wound healing, removing ammonia from the body, immune function, and the release of hormones.



Arginine is a precursor for the synthesis of nitric oxide (NO), making it important in the regulation of blood pressure.



Arginine is typically found on the outside of the protein, where the hydrophilic head group can interact with the polar environment, for example taking part in hydrogen bonding and salt bridges.



It is frequently found at the interface between two proteins.



Arginine residues in proteins can be formed into citrulline, in a post-translational modification process called citrullination.



This process is important in fetal development, is part of the normal immune process, as well as the control of gene expression, but is also significant in autoimmune diseases.



Arginine is the immediate precursor of NO.



Nitric oxide is an important signaling molecule: acts as a second messenger, as well as an intercellular messenger which regulates vasodilation, and also has functions in the immune system’s reaction to infection.



Arginine is a precursor for urea, and ornithine



Arginine is necessary for the synthesis of creatine.



L-arginine is considered a sign of a healthy endothelium.



Intravenous arginine is used in growth hormone stimulation tests because it stimulates the secretion of growth hormone.



Oral arginine increases plasma levels of L-arginine but does  not cause an increase in growth hormone.



The absorption of  more arginine may indirectly cause cold sores by disrupting the body’s balance of arginine and lysine.



L-arginine reduces blood pressure with pooled estimates of 5.4 mmHg for systolic blood pressure and 2.7 mmHg for diastolic blood pressure.



L-arginine reduces diastolic blood pressure and lengthens pregnancy for women with gestational hypertension, including women with high blood pressure as part of pre-eclampsia. 



Brain tissue of deceased schizophrenics shows altered arginine metabolism, reduced levels of γ-aminobutyric acid (GABA), but increased agmatine concentration and glutamate/GABA ratio.







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