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The cofactor product of the aromatic amino acid hydroxylases, 4a-hydroxy-6(R)-tetrahydrobiopterin, requires dehydration before tetrahydrobiopterin can be regenerated by dihydropteridine reductase. Carbinolamine dehydration occurs nonenzymatically, but the reaction is also catalyzed by 4a-hydroxytetrahydropterin dehydratase. This enzyme has the identical(More)
BACKGROUND Ireland is an example of a country that has extensive voluntary fortification with folic acid. After a public consultation process, in 2006, the Food Safety Authority in Ireland FSAI 1 recommended mandatory fortification. However due to safety considerations this decision is now on hold. Before mandatory fortification goes ahead, existing levels(More)
Numerous clinical trials using folic acid for prevention of cardiovascular disease, stroke, cognitive decline, and neural tube defects have been completed or are underway. Yet, all functions of folate are performed by tetrahydrofolate and its one-carbon derivatives. Folic acid is a synthetic oxidized form not significantly found in fresh natural foods; to(More)
Pterin-4a-carbinolamine dehydratase (PCD) is required for efficient tetrahydrobiopterin regeneration after phenylalanine hydroxylase activity. This catalytic function was proposed to be specifically defective in newborns with a mild form of hyperphenylalaninemia (HPA) and persistent high urinary levels of primapterin (7-biopterin). A second regulatory task(More)
Three conserved histidines have been shown to be important for the enzymatic activity of 4a-hydroxy-tetrahydropterin dehydratase, a bifunctional enzyme which is involved in regeneration of tetrahydrobiopterin and is also a cofactor (DCoH) for the transcription factor HNF-1alpha. The 4a isomer dependent kinetics of the mutants of rat/human enzyme, H61A,(More)
4a-Hydroxy-tetrahydrobiopterin dehydratase/DCoH is a bifunctional protein. In the cytoplasm it is an enzyme required for the regeneration of tetrahydrobiopterin, an essential cofactor for phenylalanine hydroxylase. In the nucleus it functions as a transcriptional coactivator by forming a 2:2 heterotetramer with the hepatic nuclear factor HNF1alpha (HNF1).(More)
The known functions of folate are to support one-carbon metabolism and to serve as photoreceptors for cryptochromes and photolyases. We demonstrate that 5-methyltetrahydrofolate (5-MTHF, the predominant folate in plasma) is also a potent, near diffusion limited, scavenger of singlet oxygen and quencher of excited photosensitizers. Both pathways result in(More)
The 5-amino substituents of two pyrimidine cofactors of rat liver phenylalanine hydroxylase, 2,5,6-triamino-4-pyrimidinone (TP) and 5-benzylamino-2,6-diamino-4-pyrimidinone (BDP), have been shown to be cleaved quantitatively by enzyme (Bailey, S. W., and Ayling, J. E. (1980) J. Biol. Chem. 255, 7774-7781). That the pyrimidine product of this process (when(More)