Tetrahydrobiopterin

Tetrahydrobiopterin (BH4, THB), also known as sapropterin, is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin (5-hydroxytryptamine, 5-HT), melatonin, dopamine, norepinephrine (noradrenaline), epinephrine (adrenaline), and is a cofactor for the production of nitric oxide (NO) by the nitric oxide synthases.

Structure and Biosynthesis

Tetrahydrobiopterin was discovered to act as a cofactor of phenylalanine, tyrosine, and tryptophan hydroxylases, and was subsequently found to be a cofactor of all nitric oxide synthases (NOSs). It is synthesized from GTP via two intermediates.

Function

Tetrahydrobiopterin has multiple functions in the body, most notably to convert amino acids like phenylalanine, tyrosine, and tryptophan to precursors of dopamine and serotonin. It also helps produce nitric oxide in the body.

Clinical significance

Deficiency of tetrahydrobiopterin can cause Phenylketonuria (PKU), a genetic disorder that can lead to intellectual disability, seizures, behavioral problems, and mental disorders. It can also cause Dopa-responsive dystonia (DRD), a condition that affects the nervous system, causing muscle stiffness and involuntary movements.

Treatment

Tetrahydrobiopterin can be used in the treatment of PKU and DRD. It is also being studied for its potential use in the treatment of other conditions, such as Parkinson's disease, depression, and Schizophrenia.

See also

• Biopterin
• Dihydrobiopterin reductase
• Phenylalanine hydroxylase
• Tyrosine hydroxylase
• Tryptophan hydroxylase

References

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