Catecholamines

In the synthesis pathway for the catecholamines - dopamine, epinephrine, and norepinephrine, tyrosine hydroxylase is the rate-limiting enzyme. Through alternative mRNA splicing, a wide molecular diversity of TH isoforms are generated that are tissue-specific and carry varied enzymatic activities, allowing for differential neurotransmitter availability at various synapses.

 Tyrosine hydroxylase catalyzes the rate-limiting step in the biosynthesis of the catecholamines dopamine, norepinephrine, and epinephrine. A hallmark of Parkinson's disease is the loss of dopaminergic neurons in the substantia nigra. Mutations in cases of autosomal recessive dopa-responsive dystonia and infantile Parkinsonism have also been identified recently.