citrulline

Citrulline is a crystalline amino acid with the chemical formula C₆H₁₃N₃O₃. It is formed as an intermediate in the conversion of ornithine to arginine. This process is part of the urea cycle, a metabolic pathway primarily found in mammals for excreting nitrogen. In this cycle, ornithine reacts with carbamoyl phosphate to produce citrulline. Citrulline then combines with aspartate to form argininosuccinate, which eventually yields arginine and fumarate. Arginine is then hydrolyzed to produce urea and ornithine, allowing the cycle to continue. The name "citrulline" originates from the Latin word for watermelon, Citrullus, as it was first identified in this fruit.12