Citrulline

**Semantic type:** Amino Acid, Peptide, or Protein|Pharmacologic Substance

**Definition:** A non-essential amino acid. In hepatocytes, L-citrulline is synthesized in the urea cycle by the addition of carbon dioxide and ammonia to ornithine. L-citrulline is converted into L-arginine by the enzymes argininosuccinate synthetase and argininosuccinate lyase in the presence of L-aspartate and ATP. Subsequently, L-arginine is converted to nitric oxide by nitric oxide synthase and L-citrulline is regenerated as a by-product.

**Synonyms:** - 2-Amino-5-(carbamoylamino)pentanoic Acid - CITRULLINE - L-Citrulline - N5-(Aminocarbonyl)-L-ornithine