The Stimulation of Rat Liver Phenylalanine Hydroxylase by Lysolecithin and α-Chymotrypsin

The activation of rat liver phenylalanine hydroxylase by limited proteolysis, lysolecithin, and tocopherol phosphate. Changes in conformation and catalytic properties.

Pure phenylalanine hydroxylase from rat liver can be activated by limited proteolysis with alpha-chymotrypsin. As with most other types of activation of this enzyme, including activation by exposure to lysolecithin, the increase in activity is expressed in the presence of the naturally occurring pterin cofactor, tetrahydrobiopterin, but not in the presence of synthetic pterin cofactors such as ...

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 ...

In vitro activation of rat liver phenylalanine hydroxylase by phosphorylation.

Essentially pure phenylalanine hydroxylase from rat liver can be activated between 2.5- and 3.0-fold by treatment with Mg2+, ATP, protein kinase, and cyclic AMP. The activation is seen when the hydroxylase is assayed in the presence of tetrahydrobiopterin, but not in the presence of 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine. In the presence of [gamma-32P]ATP, activation is accompanied b...

Tetrahydropterin oxidation without hydroxylation catalyzed by rat liver phenylalanine hydroxylase.