The first reaction is catalyzed by phenylalanine hydroxylase and the second reaction, which generates the reduced form of pteridine cofactor (biopterin), is catalyzed by dihydropteridine reductase (l-3). A direct assay of phenylalanine hydroxylase can be achieved by supplying optimal concentrations of reduced pteridine cofactor or an analog of the reduced cofactor (6,7-dimethyl-5,6,7,8-tetrahyd...

Effects of phenylalanine and diand tetrahydropterins on presteady-state and steady-state catalytic behavior of rat liver phenylalanine hydroxylase are analyzed. From this and previous work (Shiman, R, Xia, T., Hill, M., and Gray, D. (1994) J. BioZ. Chem. 269, 2464724656), which analyzed binding of the same compounds to the enzyme in the absence of catalysis, a model of phenylalanine hydroxylase...

Analytical ultracentrifugation has been used to analyze the oligomeric structure of the isolated regulatory domain of phenylalanine hydroxylase. The protein exhibits a monomer-dimer equilibrium with a dissociation constant of ~46 μM; this value is unaffected by the removal of the 24 N-terminal residues or by phosphorylation of Ser16. In contrast, phenylalanine binding (Kd = 8 μM) stabilizes the...

Monoclonal antibody PH7 has specificity for the phosphorylated form of the human liver phenylalanine hydroxylase and negligible reactivity towards the dephosphorylated form of the native enzyme by enzyme-linked immunoassay. PH7 binds specifically to the phosphorylated form of the liver enzyme after SDS/polyacrylamide-gel electrophoresis and transfer to nitrocellulose. Competitive blocking assay...

Rhodamine-conjugated antibodies specific for phenylalanine hydroxylase and serum albumin were employed as cytochemical probes to identify these two proteins in H4 hepatoma cells and in isolated rat hepatocytes. Each fluorescent antibody stained the cells specifically and in a distinctive manner. In both cell types, albumin staining was discretely localized in cytoplasmic and in H4 cultures vari...