Figure 1: The hydroxylation or serotonin pathway in brain and melatonin pathway in pineal. Abbreviations used are: AANAT (arylalkylamine N-acetyltransferase), ALAAD (aromatic L-amino acid decarboxylase), ALDH (aldehyde dehydrogenase), BH2 and BH4 (dihydro- and tetrahydro-biopterin), HIOMT (hydoxyindole-O-methyltransferase), MAO (monoamine oxidase), PLP (pyridoxal 5'-phosphate), TPH (tryptophan hydroxylase).