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Citrulline

 

 
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Citrulline
 
 
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The organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
 citrulline is an a-amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
. Its name is derived from citrullus, the Latin
Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
 word for watermelon
Watermelon

Watermelon refers to both fruit and plant of a vine-like herb originally from southern Africa and one of the most common types of melon. This flowering plant produces a special type of fruit known by botany as a Epigynous berry, which has a thick Peel and fleshy center ; pepos are derived from an inferior ovary and are characteristic of...
, from which it was first isolated in 1930. It has the idealized formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 H2NC(O)NH(CH2)3CH(NH2)CO2H. It is a key intermediate in the urea cycle
Urea cycle

The urea cycle is a cycle of biochemistry reactions occurring in many animals that produces urea 2carbonoxygen from ammonia . This cycle was the first metabolic cycle discovered ....
, the pathway by which mammals excrete ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
.

ulline is made from ornithine
Ornithine

Ornithine is an amino acid which plays a role in the urea cycle....
 and carbamoyl phosphate
Carbamoyl phosphate

Carbamoyl phosphate is an anion of biochemical significance. It is involved in ridding the body of excess nitrogen in the urea cycle, and also in the synthesis of pyrimidines....
 in one of the central reactions in the urea cycle.






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Encyclopedia


The organic compound
Organic compound

An organic compound is any member of a large class of chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of compounds such as carbonates, simple oxides of carbon and cyanides, as well as the allotropes of carbon, are considered Inorganic compound....
 citrulline is an a-amino acid
Amino acid

In chemistry, an amino acid is a molecule containing both amine and carboxyl functional groups. These molecules are particularly important in biochemistry, where this term refers to alpha-amino acids with the general formula H2NCHRCOOH, where R is an organic substituent....
. Its name is derived from citrullus, the Latin
Latin

Latin is an Italic language, historically spoken in Latium and Ancient Rome. Through the Military history of the Roman Empire, Latin spread throughout the Mediterranean and a large part of Europe....
 word for watermelon
Watermelon

Watermelon refers to both fruit and plant of a vine-like herb originally from southern Africa and one of the most common types of melon. This flowering plant produces a special type of fruit known by botany as a Epigynous berry, which has a thick Peel and fleshy center ; pepos are derived from an inferior ovary and are characteristic of...
, from which it was first isolated in 1930. It has the idealized formula
Chemical formula

A chemical formula is a way of expressing information about the atoms that constitute a particular chemical compound, and how the relationship between those atoms changes in chemical reactions....
 H2NC(O)NH(CH2)3CH(NH2)CO2H. It is a key intermediate in the urea cycle
Urea cycle

The urea cycle is a cycle of biochemistry reactions occurring in many animals that produces urea 2carbonoxygen from ammonia . This cycle was the first metabolic cycle discovered ....
, the pathway by which mammals excrete ammonia
Ammonia

Ammonia is a chemical compound with the chemical formula nitrogenhydrogen. It is normally encountered as a gas with a characteristic pungent odor....
.

Biosynthesis

Citrulline is made from ornithine
Ornithine

Ornithine is an amino acid which plays a role in the urea cycle....
 and carbamoyl phosphate
Carbamoyl phosphate

Carbamoyl phosphate is an anion of biochemical significance. It is involved in ridding the body of excess nitrogen in the urea cycle, and also in the synthesis of pyrimidines....
 in one of the central reactions in the urea cycle. It is also produced from arginine
Arginine

Arginine is an a-amino acid. The Optical isomerism is one of the 20 most common natural amino acids. Its codons are CGU, CGC, CGA, CGG, AGA, and AGG....
 as a by-product of the reaction catalyzed by NOS
Nitric oxide synthase

Nitric oxide synthases are present among eukaryotic enzymes as dimeric, calmodulin-dependent or calmodulin-containing cytochrome p450-like hemoprotein that combine reductase and oxygenase catalytic domains in one dimer, bear both flavin adenine dinucleotide and flavin mononucleotide , and carry out a 5`-electron oxidation of non-aromatic a...
 family (NOS; EC 1.14.13.39). Arginine is first oxidized into N-hydroxyl-arginine, which is then further oxidized to citrulline concomitant with release of nitric oxide.

Function

Although citrulline is not coded for by DNA
DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetics instructions used in the development and functioning of all known living organisms and some viruses....
 directly, several proteins are known to contain citrulline as a result of a posttranslational modification
Posttranslational modification

Posttranslational modification is the chemistry modification of a protein after its translation . It is one of the later steps in protein biosynthesis for many proteins....
. These citrulline residues are generated by a family of enzymes called peptidylarginine deiminases (PADs), which convert arginine into citrulline in a process called citrullination
Citrullination

Citrullination or deimination is the term used for the post-translational modification of the amino acid arginine in a protein into the amino acid citrulline....
 or deimination. Proteins that normally contain citrulline residues include myelin basic protein
Myelin basic protein

Myelin basic protein is a protein believed to be important in the process of myelin of nerves in the central nervous system .MBP was initially sequencing in 1979 after isolation from myelin cell membranes ....
 (MBP), filaggrin
Filaggrin

Filaggrins are filament-associated proteins which bind to keratin fibers in Epitheliums.Individuals with truncation mutations in the gene coding for filaggrin are strongly predisposed to a severe form of dry skin, , and/or eczema ....
, and several histone
Histone

In biology, histones are the chief protein components of chromatin. They act as spools around which DNA winds, and they play a role in gene regulation....
 proteins, whereas other proteins, such as fibrin
Fibrin

Fibrin is a fibrous protein involved in the clotting of blood, and is non globular. It is a fibrillar protein that is Polymerization to form a "mesh" that forms a hemostasis plug or clot over a wound site....
 and vimentin
Vimentin

Vimentin is a member of the intermediate filament family of proteins. Intermediate filaments are an important structural feature of eukaryotic cells....
 are susceptible to citrullination during cell death and tissue inflammation
Inflammation

Inflammation is the complex biological response of Blood vessel tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt by the organism to remove the injurious stimuli as well as initiate the healing process for the tissue....
.

Patients with rheumatoid arthritis
Rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic disease inflammation that may affect many tissues and organs, but principally attacks the joints producing a inflammatory synovitis that often progresses to destruction of the articular cartilage and ankylosis of the joints....
 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
Anti-citrullinated protein antibody

Anti-citrullinated protein/peptide antibodies are autoantibodies frequently detected in rheumatoid arthritis patients. Recently, these antibodies have turned up as powerful biomarkers, which are accepted as a major diagnostic tool in diagnosing rheumatoid arthritis already in a very early stage of disease....
) containing proteins or peptides is now becoming an important help in the diagnosis of rheumatoid arthritis
Rheumatoid arthritis

Rheumatoid arthritis is a chronic, systemic disease inflammation that may affect many tissues and organs, but principally attacks the joints producing a inflammatory synovitis that often progresses to destruction of the articular cartilage and ankylosis of the joints....
.

In recent studies, citrulline has been found to relax blood vessels.

Sources

Citrulline in the form of citrulline malate
Malic acid

Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. This dicarboxylic acid is the active ingredient in many sour or tart foods....
 is sold as a performance-enhancing athletic dietary supplement
Dietary supplement

A dietary supplement, also known as food supplement or nutritional supplement, is a preparation intended to provide nutrients, such as vitamins, Dietary minerals, fatty acids or amino acids, that are missing or are not consumed in sufficient quantity in a person's diet ....
 which is said to reduce muscle fatigue.

The rind of watermelon
Watermelon

Watermelon refers to both fruit and plant of a vine-like herb originally from southern Africa and one of the most common types of melon. This flowering plant produces a special type of fruit known by botany as a Epigynous berry, which has a thick Peel and fleshy center ; pepos are derived from an inferior ovary and are characteristic of...
 (Citrullus lanatus) is a good natural source of citrulline.

See also

  • Citrullinemia
    Citrullinemia

    Citrullinemia, also called citrullinuria, is an autosomal recessive urea cycle disorder that causes ammonia and other toxic substances to accumulate in the blood....