Direct inhibition of tyrosine hydroxylase activity by catechol estrogens

Catechol estrogens, the 2-hydroxylated metabolites of estrogens, recently shown to be formed in brain, inhibit tyrosine hydroxylase, the enzyme that catalyzes the pivotal step in the biosynthesis of the neurotransmitters dopamine and norepinephrine. The nature of the inhibition is by competition with the pterin cofactor and thus resembles feedback inhibition of the enzyme by catecholamines.