Melatonin is an important regulator of circadian rythmus and influences also insulin secretion, immune function, retinal function and neuroprotection. The synthesis starts with the amino acid tryptophan which is catalyzed to serotonin. AANAT and ASMT catalyze the reaction to N-acetylserotonin and melatonin, respectively. Melatonin is mainly discarded by the liver enzyme CYP1A2 but other enzymes from the cytochrome family are also known to metabolize melatonin. Recent investigation show e.g. that melatonin plays an important role in colon cancer growth.
Proteins on this pathway have targeted assays available via the [CPTAC Assay Portal](https://assays.cancer.gov/available_assays?wp_id=WP3298).