The organic compound citrulline is a non-essential α-amino acid. and further codified in 1930.
Citrulline has the formula H<sub>2</sub>NC(O)NH(CH<sub>2</sub>)<sub>3</sub>CH(NH<sub>2</sub>)CO<sub>2</sub>H.
Biosynthesis
Citrulline can be derived from:
- from arginine via nitric oxide synthase, as a byproduct of the production of nitric oxide for signaling purposes It is also prevalent in trichohyalin at the inner root sheath and medulla of hair follicles, where it is synthesized from arginine. Arginine is first oxidized into N-hydroxyl-arginine, which is then further converted to citrulline concomitant with release of nitric oxide.
Several proteins contain citrulline as a result of a post-translational modification. These citrulline residues are generated by a family of enzymes called peptidylarginine deiminases, which convert arginine into citrulline in a process called citrullination or deimination with the help of calcium ions.
Uses
L-citrulline is sold as a dietary supplement. Citrulline has not been approved as a prescription drug, has no confirmed clinical uses, and remains under preliminary research, as of 2026.
See also
- Citrullinemia