tyrosiinihydroksylaasi

Tyrosiinihydroksylaasi, often abbreviated as TH, is a crucial enzyme in the biosynthesis of catecholamines. Its primary role is to catalyze the conversion of L-tyrosine to L-DOPA, also known as levodopa. This is the rate-limiting step in the production of dopamine, norepinephrine, and epinephrine, which are vital neurotransmitters and hormones.

The enzyme is a monooxygenase and requires molecular oxygen, ferrous iron (Fe2+), and tetrahydrobiopterin (BH4) as cofactors. TH is found in the adrenal medulla, sympathetic neurons, and the central nervous system. Its activity is tightly regulated by various mechanisms, including feedback inhibition by the end-product catecholamines and phosphorylation by different kinases, which can alter its sensitivity to these inhibitors.

Genetic mutations in the TH gene can lead to severe neurological disorders, such as aromatic L-amino acid decarboxylase deficiency, which is characterized by profound neurological impairment. The importance of TH in catecholamine synthesis makes it a significant target for research and therapeutic interventions, particularly in conditions like Parkinson's disease where dopamine levels are depleted.