these properties of bovine pineal tryptophan hydroxylase are distinguishable from those of the hydroxylase in the brain indicating that the hydroxylation of tryptophan in the brain leading to the synthesis of serotonin and the reaction in the pineal gland leading to the formation of melatonin are catalyzed by different tryptophan hydroxylases and are probably under separate regulatory mechanisms .
C0020364
hydroxylase
C0041252
tryptophan hydroxylases