Liver phenylalanine hydroxylase assay

Liver phenylalanine hydroxylase assay.

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...

Regulation of Rat Liver Phenylalanine Hydroxylase

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...

Rat liver phenylalanine hydroxylase, an iron enzyme.

Phenylalanine hydroxylase that is essentially pure contains 1 to 2 moles of iron per mole of enzyme (assuming a molecular weight of 100,000). Electron spin resonance (ESR) studies have shown that the iron is present in the high spin ferric form. The addition of substrates (i.e. phenylalanine and dimethyltetrahydropterin) causes the signal for this form to disappear. The iron, 50 to 80%, can be ...

Avoiding artifactual errors in assay of phenylalanine hydroxylase.

334 CLINICAL CHEMISTRY, Vol. 25, No. 2, 1979 is used at pH 7.4 and the fact that this interference depends on the type of tracer and pH at which the assay is performed are significant. Also the observation that the introduction of an ethanol precipitation step into the assay eliminates the effect of variation in the matrixes of commercial standards provides for a significant improvement in the ...

Phenylalanine Hydroxylase, Tyrosine Hydroxylase, and Tryptophan Hydroxylase