What is "citrulline"

citrulline \citrulline\ n. an amino acid that is an intermediate in the conversion of ornithine to arginine.

n. (context amino acid English) An amino acid, first isolated from watermelons, that is an intermediate in the urea cycle

n. an amino acid that does not occur in proteins but is an intermediate in the conversion of ornithine to arginine

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 1914 by Koga & Odake. It was finally identified by Wada in 1930. It has the formula HNC(O)NH(CH)CH(NH)COH. It is a key intermediate in the urea cycle, the pathway by which mammals excrete ammonia.

In the body, citrulline is produced as a byproduct of the enzymatic production of nitric oxide from the amino acid arginine, catalyzed by nitric oxide synthase. This is an essential reaction in the body because nitric oxide is an important vasodilator required for regulating blood pressure.