Enables tyrosine 3-monooxygenase activity. Involved in several processes, including cellular response to amphetamine; dopamine biosynthetic process from tyrosine; and male mating behavior. Located in axon. Expressed in dopaminergic neurons; socket cell; and in male. Used to study several diseases, including amphetamine abuse; cocaine abuse; and nicotine dependence. Human ortholog(s) of this gene implicated in several diseases, including Parkinsonism; artery disease (multiple); and obesity. Is an ortholog of human TH (tyrosine hydroxylase).