Dopamine β-hydroxylase (Dopamine beta-hydroxylase, Dopamine beta-monooxygenase) is an enzyme that in humans is encoded by the DBH gene. Dopamine β-monooxygenase catalyzes the chemical reaction with 3 substrates of 3,4-dihydroxyphenethylamine, ascorbate, and O2, whereas its 3 products are noradrenaline, dehydroascorbate, and H2O. Dopamine β-hydroxylase belongs to the family of oxidoreductases, specifically those acting on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. Dopamine β-hydroxylase participates in tyrosine metabolism. Dopamine β-hydroxylase has 3 cofactors: copper, PQQ, and Fumarate. Dopamine β-hydroxylase is in the catecholamine biosynthetic pathway. Dopamine β-hydroxylase has been shown to be associated with decision making and addictive behaviors such as alcohol and smoking, attention deficit hyperactivity disorder, and also with neurological diseases such as Schizophrenia and Alzheimer's.