Tyrosine hydroxylase

Tyrosine hydroxylase (TH) is an enzyme that is involved in the process of neurotransmitter synthesis. It is responsible for catalyzing the conversion of the amino acid tyrosine to L-DOPA, which is a precursor to the neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline).

Function

Tyrosine hydroxylase plays a crucial role in the physiology of adrenergic neurons. It is the rate-limiting enzyme in the synthesis of catecholamines, determining the production rate of these critical neurotransmitters. Dysregulation of this enzyme's activity is associated with various neurological disorders, including Parkinson's disease and schizophrenia.

Structure

The enzyme is a tetramer composed of four identical subunits. Each subunit contains a catalytic domain and a regulatory domain. The catalytic domain is responsible for the enzyme's enzymatic activity, while the regulatory domain controls the enzyme's activity.

Regulation

The activity of tyrosine hydroxylase is regulated at several levels, including transcriptional regulation, post-translational modifications, and feedback inhibition by its end products. The enzyme is also regulated by phosphorylation and dephosphorylation, processes that modulate the enzyme's activity.

Clinical significance

Alterations in the function of tyrosine hydroxylase have been implicated in a number of neurological disorders. For example, a decrease in the activity of this enzyme is associated with Parkinson's disease, a neurodegenerative disorder characterized by the loss of dopamine-producing neurons. On the other hand, an increase in the activity of tyrosine hydroxylase is associated with schizophrenia, a psychiatric disorder characterized by abnormal dopamine activity.

See also

• Dopamine
• Parkinson's disease
• Schizophrenia
• Neurotransmitter

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