To the Editor: Tetrahydrobiopterin (BH4)-responsive phenylalanine hydroxylase (PAH) deficiency is a recently recognized variant of hyperphenylalaninemia (HPA) characterized by a positive response to a BH4-loading test (1). Up to the present time, 11 different mutations have been described which are associated with mild HPA (Table 1) and all patients have been shown to be compound heterozygotes ...

This work had two purposes: (i) to determine in vivo whether liver phenylalanine hydroxylase (PAH) is regulated by its substrates phenylalanine and tetrahydrobiopterin (BH4) as studies with purified enzyme suggest and (ii) to investigate in vivo the relationship between PAH activity and BH4 turnover. We found there are two BH4 pools in hepatocytes, one that is metabolically available (free BH4)...

Phenylketonuria (PKU) is a metabolic disease causing increased levels of phenylalanine in blood and body fluids. Circulating phenylalanine is normally cleared by phenylalanine hydroxylase (PAH) expressed in the liver. The aim of this study is to exploit the skin as a 'metabolic sink' removing phenylalanine from the blood. We have previously showed that the overexpression of PAH and GTP cyclohyd...

Phenylalanine hydroxylase (PAH) is a key tyrosine-biosynthetic enzyme involved in neurological and melanin-associated physiological processes. Despite extensive investigations in holometabolous insects, a PAH contribution to insect embryonic development has never been demonstrated. Here, we have characterized, for the first time, the PAH gene in a hemimetabolous insect, the aphid Acyrthosiphon ...

AIM Phenylalanine hydroxylase (PAH) deficiency is caused by mutations in the PAH gene resulting in a primary deficiency of the PAH enzyme activity, intolerance to the dietary intake of phenylalanine (Phe), and production of the phenylketonuria disease. To date there have been no reports on the molecular analysis of phenylketonuria in the Iranian Azeri Turkish population. In this study, a total ...

Human phenylalanine hydroxylase (PAH) catalyzes the conversion of L-phenylalanine to L-tyrosine. Deficiency of this enzyme results in phenylketonuria, a common genetic disorder of amino acid metabolism that causes severe mental retardation. In primates, PAH is expressed specifically in the liver, while in rodents PAH activity is also present in kidney, although at a much lower level. A 9-kiloba...

A significant share of patients with phenylalanine hydroxylase (PAH) deficiency benefits from pharmacological doses of tetrahydrobiopterin (BH(4)), the natural PAH cofactor. Phenylketonuria (PKU) is hypothesized to be a conformational disease, with loss of function due to protein destabilization, and the restoration of enzyme function that is observed in BH(4) treatment might be transmitted by ...

Abstract Phenylketonuria (PKU) is caused by autosomal recessive variants in phenylalanine hydroxylase ( PAH ), leading to systemic accumulation of L-phenylalanine (L-Phe) that may reach neurotoxic levels. A homozygous Pah - R261Q mouse, with a highly prevalent misfolding variant humans, reveals the expected hepatic activity decrease, L-Phe increase, L-tyrosine and L-tryptophan tetrahydrobiopter...

Metabolic diseases arise from mutations in key enzymes of major metabolic pathways. One promising approach for the treatment of such diseases is based on the administration of a wild-type enzyme to substitute the activity of the impaired enzyme by the use of enzyme replacement therapy, yet it is important to deliver this enzyme to the specific deficient tissue. We suggest a new concept for the ...