Precursor to tetrahydrobiopterin, a required cofactor for a number of enzymes, including the biosynthesis of l-tyrosine; the inability to synthesize dihydrobiopterin can result in a form of malignant hyperphenylalaninemia.
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Tetrahydrobiopterin (BH4) is one of the critical cellular non-enzymatic redox sensitive antioxidants and oxidation of BH4 to dihydrobiopterin (BH2) and other oxidized bio-pterin species causes endothelial nitric oxide synthases (eNOS) to produce higher superoxide levels instead of nitric oxide (NO), a phenomenon popularly termed as "eNOS uncoupling" resulting in increased oxidative stress (Crabtree et al.
NO synthase uncoupling in the kidney of Dahl S rats: role of dihydrobiopterin," Hypertension, vol.
For analysis of plasma levels of biopterin, dihydrobiopterin (BH2) and tetrahydrobiopterin (BH4), we used reversed phase HPLC with electrochemical detection and fluorescence detection.
61), including that of biopterin, (Biop in the urine, columns 2 & 3), dihydrobiopterin (BH2, columns 4 & 5), tetrahydrobiopterin (BH4, columns 6 & 7), the enzyme GTP cyclohydrolase I in lymphocytes (GPCH, columns 8 & 9), 3-nitrotyrosine (3-NT, columns 10 & 11), and neopterin in the urine (Neo, columns 12 & 13).
In aged vessels, endothelial dysfunction occurs owing to eNOS uncoupling by reducing the tetrahydrobiopterin to dihydrobiopterin ratio [22].
In the presence of 5-MTHF, the enzyme dihydrobiopterin reductase can reduce quininoid dihydrobiopterin to tetrahydrobiopterin (BH4) (12).
c) Ratio of reduced tetrahydrobiopterin (BH4) to oxidized dihydrobiopterin (BH2) in mouse serum as measure of systemic oxidative stress is shown.
4] is oxidized to quinonoid dihydrobiopterin and is recycled to BH4 by pterin-4[alpha]-carbinolamine dehydratase (EC 4.