1. Plasma tyrosine and phenylalanine were measured in patients with chronic renal failure and in normal subjects. Plasma tyrosine to phenylalanine ratio was greatly decreased in patients with creatinine clearance less than 16 ml/min, suggesting an impairment of phenylalanine hydroxylation. This ratio correlated with the percentage of essential to total amino nitrogen in the plasma. 2. Phenylala...

The mode of action of the p-chlorophenylalanine in these animals is not clear. pChlorophenylalanine, in vitro, is not an appreciable inhibitor of phenylalanine hydroxylase, and this is apparently so in vivo also as the lowering of phenylalanine hydroxylase activity shows a delayed response to p-chlorophenylalanine treatment. However, the decrease in phenylalanine hydroxylase activity is not cau...

The brain damage which occurs in untreated phenylketonuria probably results from the high plasma phenylalanine concentration prevailing in this condition, as treatment with a low-phenylalanine diet mitigates the situation. The actual cause of the brain damage is not known, but investigations have been carried out with high phenylalanine loads to simulate phenylketonuria and so elucidate the nat...

Pseudomonas species ATCC 11299a synthesizes tyrosine via an inducible phenylalanine hydroxylase when grown on phenylalanine or tyrosine as a carbon source (G. Guroff and T. Ito, Biochim. Biophys. Acta 77:159, 1963; J. Biol. Chem. 240:1175, 1965). A second pathway to tyrosine synthesis involving transamination between glutamic acid or phenylalanine and p-hydroxyphenylpyruvic acid has been detect...

Pheochromocytoma tyrosine hydroxylase was reported to have unusual catalytic properties, which might be unique to the tumor enzyme (Dix, T. A., Kuhn, D. M., and Benkovic, S. J. (1987) Biochemistry 24, 3354-3361). Two such properties, namely the apparent inability to hydroxylate phenylalanine and an unprecedented reactivity with hydrogen peroxide were investigated further in the present study. T...

Glyceryl ether monooxygenase is a tetrahydrobiopterin-dependent membrane-bound enzyme which catalyses the cleavage of lipid ethers into glycerol and the corresponding aldehyde. Despite many different characterisation and purification attempts, so far no gene and primary sequence have been assigned to this enzyme. The seven other tetrahydrobiopterin-dependent enzymes can be divided in the family...

Activation of rat liver phenylalanine hydroxylase by limited proteolysis catalyzed by chymotrypsin was investigated with the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high pressure gel filtration. Both activation and proteolysis were decreased by the addition of the natural cofactor, (6R)-tetrahydrobiopterin. From chymotryptic digests of the hydroxylase carried out in...

Phenylketonuria (PKU) is one of the most common metabolic inborn diseases caused by mutations in the phenylalanine hydroxylase (PAH) gene. This gene is linked to a variable number of tandem repeats (VNTR) region which is a polymorphic marker that facilitates the implementation of prenatal diagnosis and carrier screening. In this study, VNTR with 13 repeats that has not been reported previously ...