What is the Biopterin pathway?
Biopterin synthesis occurs through two principal pathways; the de novo pathway involves three enzymatic steps and proceeds from GTP, while the salvage pathway converts sepiapterin to biopterin. BH4 is the principal active cofactor, and a recycling pathway converts BH2 to BH4.
What is the importance of Biopterin?
Biopterin is an important co-enzyme for breaking down amino acids, especially the amino acid phenylalanine. BIOPT-BS occurs when the body cannot make its own BH4, the substance from which biopterin is made. Babies with BIOPT-BS either do not produce enough or produce non-working enzymes for making BH4.
What is the function of phenylalanine?
Function: The essential amino acid L-phenylalanine (Phe) is needed for the synthesis of proteins, catecholamines, and melanin; it is also an important precursor of the amino acid L-tyrosine (Tyr).
What is the role of tetrahydrobiopterin?
Tetrahydrobiopterin (BH4, THB), also known as sapropterin (INN), 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 ( …
What enzyme requires tetrahydrobiopterin as a cofactor?
Tetrahydrobiopterin is an essential cofactor for the neurotransmitter synthesizing enzymes tyrosine hydroxylase (which catalyzes the conversion of tyrosine to l-dopa) and tryptophan hydroxylase (which catalyzes the conversion of tryptophan to 5-hydroxytryptophan [5-HTP]), as well as for phenylalanine hydroxylase (which …
What is H4 Biopterin?
Tetrahydrobiopterin (H4-biopterin) is an essential cofactor of a set of enzymes that are of central metabolic importance, i.e. the hydroxylases of the three aromatic amino acids phenylalanine, tyrosine, and tryptophan, of ether lipid oxidase, and of the three nitric oxide synthase (NOS) isoenzymes.
What is BH4 deficiency?
Tetrahydrobiopterin deficiency is a rare disorder characterized by a shortage (deficiency) of a molecule called tetrahydrobiopterin or BH4. This condition alters the levels of several substances in the body, including phenylalanine.
How does phenylalanine affect the body?
Phenylalanine can cause intellectual disabilities, brain damage, seizures and other problems in people with PKU . Phenylalanine occurs naturally in many protein-rich foods, such as milk, eggs and meat. Phenylalanine is also sold as a dietary supplement.
What is BH2 and BH4?
BH2 is converted back to BH4 To avoid production of superoxide, BH2 in the body is rapidly converted back into BH4 through the action of the enzyme dihydropteridine reductase (QPDR). QDPR is the enzyme which typically converts BH2 back into BH4, however the enzyme DHFR has also shown a similar activity.
Is Tetrahydrobiopterin a vitamin?
General information. Tetrahydrobiopterin is a naturally occurring nutrient and an essential co-factor of enzymes involved in the biosynthesis of 5-hydroxytryptamine (5HT, serotonin), dopamine, noradrenaline (norepinephrine), adrenaline (epinephrine), melatonin, and nitric oxide [1].
How does tetrahydrobiopterin help process phenylalanine?
Tetrahydrobiopterin normally helps process several amino acids, including phenylalanine. It is also involved in the production of neurotransmitters. If one of the enzymes fails to function correctly because of a gene mutation, little or no tetrahydrobiopterin is available to help process phenylalanine.
What is the role of the cofactor BH4 in phenylalanine hydroxylase?
BH4 is an essential cofactor not only for phenylalanine hydroxylase, but also for tyrosine and two tryptophan hydroxylases, three nitric oxide synthases, and glyceryl-ether monooxygenase.
What is the source of phenylalanine?
Phenylalanine is a building block of proteins (an amino acid) that is obtained through the diet. It is found in foods that contain protein and in some artificial sweeteners. High levels of phenylalanine are present from early infancy in people with untreated tetrahydrobiopterin deficiency.
What are the causes of tetrahydrobiopterin deficiency?
Tetrahydrobiopterin deficiency can be caused by mutations in one of several genes, including GCH1, PCBD1, PTS, and QDPR. These genes provide instructions for making enzymes that help produce and recycle tetrahydrobiopterin in the body. Tetrahydrobiopterin normally helps process several amino acids, including phenylalanine.
