Tryptophan, an essential amino acid, serves as a building block for protein and a precursor to several molecules. Other than its role as a protein component, tryptophan is the starting substrate for two major pathways: the serotonin–melatonin pathway and the kynurenine pathway. These pathways produce metabolites that regulate mood, circadian rhythm, immune tolerance, oxidative stress, and energy metabolism. Tryptophan is converted to serotonin, particularly in the gut and brain, affecting neurotransmission, appetite, pain perception, and stress responses. It is further converted to melatonin in the pineal gland, affecting sleep–wake cycle regulation. Tryptophan is catabolized by the kynurenine pathway, thus modulating the immune response. Dysregulation is implicated in neurodegenerative disease, resulting in neuroinflammation and excitotoxicity, as well as mood disturbances, sleep disorders and cognitive and physical impairments. AkrivisBio’s Tryptophan Assay is a simple, sensitive way to measure tryptophan in a variety of biological samples with a sensitivity below 250 picomoles
