Conversion of L‐tryptophan to serotonin and melatonin in human melanoma cells

We showed in human melanoma cells tryptophan hydroxylase (TPH) and hydroxyindole methyltransferase genes expression with the sequential enzymatic activities of TPH, serotonin (Ser) N ‐acetyltransferase and hydroxyindole methyltransferase. The presence of the products Ser, 5OH‐tryptophan, N ‐acetylserotonin, melatonin (Mel), 5‐methoxytryptamine and 5‐methoxytryptophol was documented by liquid chromatography–mass spectrometry. Thus, human melanoma cells can synthesize and metabolize Ser and Mel.