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C6H13O3N3 An amino acid formed in the synthesis of arginine from ornithine.



(also called α-amino-δ-ureidovaleric acid), H2NCONH(CH2)3CH(NH2)COOH, a natural amino acid.

Citrulline exists in the optically active L- and D-forms and in the racemic DL-form. L-citrulline is found as a free compound in the juice of watermelons and a number of other plants, in the tubers of legumes, and in the tissues of mammals (liver, kidney, brain, muscles, and blood). Citrulline is not a component of natural proteins. Citrulline is separated from enzymatic hydrolysates of casein as a result of arginine splitting. In many organisms, citrulline participates in the ornithine cycle, in which it serves as an intermediate in the biosynthesis of arginine from ornithine. In plants, citrulline also participates in nitrogen fixation.


Meister, A. Biokhimiia aminokislot. Moscow, 1961. (Translated from English.)
Lehninger, A. Biokhimiia: Molekuliarnye osnovy struktury i funktsii kletki. Moscow, 1976. (Translated from English.)