The phosphorylation of human phenylalanine hydroxylase by cyclic AMP-dependent protein kinase was studied using recombinant enzyme expressed as a fusion protein in the pMAL system of Escherichia coli. Using the target sequence of the restriction protease enterokinase (Asp4-Lys) as the linker peptide, 100% full-length human phenylalanine hydroxylase was obtained on protease cleavage. The fusion ...

A sensitive method was developed for determining the phenylalanine hydroxylase activity of crude tissue preparations in the presence of optimum concentrations of the 6,7-dimethyl-5,6,7,8-tetrahydropterin cofactor (with ascorbate or dithiothreitol to maintain its reduced state) and substrate. Tissue distribution studies showed that, in addition to the liver, the kidney also contains significant ...

A monoclonal antibody (PH 7), which recognizes the phosphorylated form of phenylalanine hydroxylase from human liver, has been used for the analysis of the enzyme in crude cell extracts from rat. In immunoblot analyses of rat liver cell extracts, the extent of binding of PH 7 closely correlates with the phosphorylation state of phenylalanine hydroxylase, as judged by [32P]Pi incorporation. Thes...

An extract from a liver biopsy of a patient with classical phenylketonuria contains phenylalanine 4-hydroxylase (EC 1.14.3.1) with a specific activity 0.27% of the normal activity of the hydroxylase. This enzyme from a patient with phenylketonuria is a structurally altered form of phenylalanine 4-hydroxylase that probably results from a mutation in the gene coding for the hydroxylase.

Phenylketonuria is the most prevalent disorder caused by an inborn error in aminoacid metabolism. It results from mutations in the phenylalanine hydroxylase gene. Phenotypes can vary from a very mild increase in blood phenylalanine concentrations to a severe classic phenotype with pronounced hyperphenylalaninaemia, which, if untreated, results in profound and irreversible mental disability. Neo...

The laboratory mouse represents an important model for the study of phenylalanine metabolism and the pathochemistry of phenylketonuria, yet mouse phenylalanine hydroxylase (PAH) has not been extensively studied. We report the cloning and sequencing of a mouse PAH cDNA, the expression of enzymic activity from the mouse PAH cDNA clone and the identification of mouse PAH and human PAH by two-dimen...

The enzymic hydroxylation of phenylalanine by phenylalanine hydroxylase (E.C. 1.14.16.1.) in vitro is dependent on the presence of hydrogen peroxide removing processes. The loss of phenylalanine hydroxylase activity can be prevented to the same extent by catalase as well as the presence of optimized amounts of both peroxidase and superoxide dismutase. Peroxidase alone exhibited only two third o...

A method was developed to study the unsupplemented phenylalanine hydroxylase system in rat liver slices. All of the components of the systemtetrahydrobiopterin, dihydropteridine reductase, and the hydroxylase itself-are present under conditions which should be representative of the actual physiological state of the animal. The properties of the system in liver slices have been compared to those...