Citrulline

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Citrulline
Systematic (IUPAC) name
2-amino-5-(carbamoylamino)pentanoic acid
Identifiers
CAS number	372-75-8
PubChem	9750
Chemical data
Formula	C6H13N3O3
Molar mass	175.2
Complete data

The organic compound citrulline is an α-amino acid. Its name is derived from citrullus, the Latin word for watermelon, from which it was first isolated in 1930.^[1] It has the idealized formula H₂NC(O)NH(CH₂)₃CH(NH₂)CO₂H. It is a key intermediate in the urea cycle, the pathway by which mammals excrete ammonia.

Contents 1 Biosynthesis 2 Function 3 Dietary supplement 4 See also 5 References 6 External links

[edit] Biosynthesis

Citrulline is made from ornithine and carbamoyl phosphate in one of the central reactions in the urea cycle. It is also produced from arginine as a by-product of the reaction catalyzed by NOS family (NOS; EC 1.14.13.39).^[2] Arginine is first oxidized into N-hydroxyl-arginine, which is then further oxidized to citrulline concomitant with release of nitric oxide.

[edit] Function

Although citrulline is not coded for by DNA directly, several proteins are known to contain citrulline as a result of a posttranslational modification. These citrulline residues are generated by a family of enzymes called peptidylarginine deiminases (PADs), which convert arginine into citrulline in a process called citrullination or deimination. Proteins that normally contain citrulline residues include myelin basic protein (MBP), filaggrin, and several histone proteins, whereas other proteins, such as fibrin and vimentin are susceptible to citrullination during cell death and tissue inflammation.

Patients with rheumatoid arthritis often have detectable antibodies against proteins containing citrulline. Although the origin of this immune response is not known, detection of antibodies reactive with citrulline (anti-citrullinated protein antibodies) containing proteins or peptides is now becoming an important help in the diagnosis of rheumatoid arthritis.^[3]

[edit] Dietary supplement

Citrulline in the form of citrulline malate is sold as a performance-enhancing athletic dietary supplement which is said to reduce muscle fatigue. [1]

[edit] See also

• Citrullinemia

[edit] References

1. ^ Wada, M. (1930). "Über Citrullin, eine neue Aminosäure im Presssaft der Wassermelone, Citrullus vulgaris Schrad.". Biochem. Zeit. 224: 420. 
2. ^ Nelson, D. L.; Cox, M. M. "Lehninger, Principles of Biochemistry" 3rd Ed. Worth Publishing: New York, 2000. ISBN 1-57259-153-6.
3. ^ Coenen D, Verschueren P, Westhovens R, Bossuyt X (March 2007). "Technical and diagnostic performance of 6 assays for the measurement of citrullinated protein/peptide antibodies in the diagnosis of rheumatoid arthritis". Clin. Chem. 53 (3): 498–504. doi:10.1373/clinchem.2006.078063. PMID 17259232. 

[edit] External links