Biopterin (BioDeep_00000017782)

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Biopterin concentrations in cerebrospinal fluid from patients with Parkinsons disease, in which the nigrostriatal dopamine neurons degenerate, are lower than those from age-matched older controls. In hereditary progressive dystonia/DOPA-responsive dystonia, which is a dopamine deficiency caused by mutations in GTP cyclohydrolase I without neuronal cell death (Segawas disease), biopterin in cerebrospinal fluid decrease in parallel owing to the decreased activity in GTP cyclohydrolase I (EC 3.5.4.16, is an enzyme that is part of the folate and biopterin biosynthesis pathways. It is responsible for the hydrolysis of guanosine triphosphate (GTP) to form 7,8-dihydroneopterin 3-triphosphate. (Pteridines (1999), 10(1), 5-13.) Lowered levels of urinary biopterin concomitant with elevated serum phenylalanine concentration occur in a variant type of hyperphenylalaninemia caused by a deficiency of tetrahydrobiopterin (BH4), the obligatory cofactor for phenylalanine hydroxylase. The most frequent form of this cofactor deficiency is due to lack of 6-pyruvoyl-tetrahydropterin synthase (PTPS) activity, the second enzyme in the biosynthetic pathway for BH4. (PMID 8178819) The hepatic phenylalanine hydroxylating system consists of 3 essential components, phenylalanine hydroxylase, dihydropteridine reductase, and the nonprotein coenzyme, tetrahydrobiopterin. The reductase and the pterin coenzyme are also essential components of the tyrosine and tryptophan hydroxylating systems. There are 3 distinct forms of phenylketonuria or hyperphenylalaninemia, each caused by lack of 1 of these essential components. The variant forms of the disease that are caused by the lack of dihydropteridine reductase or tetrahydrobiopterin are characterized by severe neurol. deterioration, impaired functioning of tyrosine and tryptophan hydroxylases, and the resultant deficiency of tyrosine- and tryptophan-derived monoamine neurotransmitters in brain. (PMID 3930837) [HMDB]
Biopterin, also known as tetrahydrobiopterin or BH4, belongs to the class of organic compounds known as biopterins and derivatives. These are coenzymes containing a 2-amino-pteridine-4-one derivative. Biopterin or tetrahydrobiopterin is also classified as a pterin derivative that consists of pterin group bearing an amino, an oxo and a 1,2-dihydroxypropyl substituent at positions 2, 4 and 6, respectively. Biopterin compounds found within the animals include BH4 (tetrahydrobiopterin), the free radical BH3, and BH2 (also a free radical, called Dihydrobiopterin). BH2 is produced in the synthesis of L-DOPA, dopamine, norepinephrine and epinephrine. It is restored to the required cofactor tetrahydrobiopterin by the enzyme dihydrobiopterin reductase. Tetrahydrobiopterin (BH4) is a 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). It is also a cofactor for the production of nitric oxide (NO) by the nitric oxide syntheses. Tetrahydrobiopterin is biosynthesized from guanosine triphosphate (GTP) by three chemical reactions mediated by the enzymes GTP cyclohydrolase I (GTPCH), 6-pyruvoyltetrahydropterin synthase (PTPS), and sepiapterin reductase (SR). Biopterin synthesis disorders are a cause of hyperphenylalaninemia. There are 3 distinct forms of phenylketonuria or hyperphenylalaninemia, each caused by lack of aromatic amino acid hydroxylase enzymes. The variant forms of hyperphenylalaninemia that are caused by the lack of dihydropteridine reductase or tetrahydrobiopterin are characterized by severe neurological deterioration, impaired functioning of tyrosine and tryptophan hydroxylases, and the resultant deficiency of tyrosine- and tryptophan-derived monoamine neurotransmitters in brain. (PMID 3930837).
6-Biopterin (L-Biopterin), a pterin derivative, is a NO synthase cofactor.

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