Tyrosine hydroxylase

The conversion of tyrosine to L-DOPA by tyrosine hydroxylase.

Tyrosine hydroxylase is an enzyme that is crucial in the biosynthesis of catecholamines. It catalyzes the conversion of the amino acid tyrosine to L-DOPA, which is the precursor to important neurotransmitters such as dopamine, norepinephrine, and epinephrine.

Structure

Structure of tyrosine hydroxylase from rat, showing two of its domains.

Tyrosine hydroxylase is a tetrameric enzyme, meaning it is composed of four subunits. Each subunit contains a catalytic domain and a regulatory domain. The enzyme requires a cofactor, tetrahydrobiopterin, and molecular oxygen to function. The catalytic domain is responsible for the hydroxylation of tyrosine, while the regulatory domain modulates the enzyme's activity.

Function

Tyrosine hydroxylase is the rate-limiting enzyme in the synthesis of catecholamines. It is primarily found in the central nervous system, particularly in the substantia nigra and locus coeruleus, as well as in the adrenal medulla. The enzyme's activity is regulated by various factors, including phosphorylation and feedback inhibition by catecholamines.

Clinical Significance

Dysregulation of tyrosine hydroxylase activity is associated with several neurological disorders. For instance, reduced activity of the enzyme can lead to dopamine deficiency, contributing to conditions such as Parkinson's disease. Conversely, overactivity may be involved in hypertension due to excessive production of norepinephrine.

Research and Applications

Immunofluorescence image showing serotonin transporter in green, tyrosine hydroxylase in red, and nuclear DNA in blue in a region of rat brain.

Research on tyrosine hydroxylase has provided insights into the treatment of neurological disorders. Inhibitors of the enzyme are being explored as potential therapeutic agents for conditions characterized by excessive catecholamine production. Additionally, understanding the regulation of tyrosine hydroxylase can aid in developing strategies to enhance dopamine production in neurodegenerative diseases.

Related Pages

• Dopamine
• Norepinephrine
• Epinephrine
• Parkinson's disease
• Catecholamine

References

• 
  Catecholamines biosynthesis