Tryptophan

**Semantic type:** Amino Acid, Peptide, or Protein

**Definition:** The least plentiful of all 22 amino acids and an essential amino acid in humans (provided by food), Tryptophan is found in most proteins and a precursor of serotonin. Tryptophan is converted to 5-hydroxy-tryptophan (5-HTP), converted in turn to serotonin, a neurotransmitter essential in regulating appetite, sleep, mood, and pain. Tryptophan is a natural sedative and present in dairy products, meats, brown rice, fish, and soybeans. (NCI04)

**Synonyms:** - (S)-2-Amino-3-(1H-indol-3-yl)-propanoic acid - TRYPTOPHAN - Trp