or tyrosine 3-monooxygenase
is the enzyme
responsible for catalyzing the conversion of the amino acid L-tyrosine
(DOPA). It does so using tetrahydrobiopterin
as a coenzyme
. DOPA is a precursor for dopamine
, which, in turn, is a precursor for norepinephrine
(noradrenaline) and epinephrine
(adrenaline). In humans, tyrosine hydroxylase is encoded by the TH gene
The enzyme, an oxygenase
, is found in the cytosol
of all cells containing catecholamines
. This initial reaction is the rate limiting step
in the production of catecholamines.
The enzyme is highly specific, not accepting indole
derivatives - which is unusual as many other enzymes involved in the production of catecholamines do.
Tyrosine hydroxylase can be inhibited by the drug α-methyl-para-tyrosine (Metirosine
). This inhibition can lead to a depletion of dopamine and norepinepherine in the brain due to the lack of the precursor L-Dopa (L-3,4-dyhydroxyphenylalanine) which is synthesized by tyrosine hydroxylase. This drug is rarely used and can cause depression, but it is useful in treating pheochromocytoma
and also resistant hypertension
Tyrosine hydroxylase is an autoantigen in Autoimmune Polyendocrine Syndrome ......