title: In vitro activation of rat liver phenylalanine hydroxylase by phosphorylation.
abstract: 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 by incorporation of 32P into the protein to the extent of 0.7 mol/mol of hydroxylase subunit (Mr = 50,000). Cehmical analysis of the untreated enzyme shows that it already contains about 0.3 mol of Pi/mol of hydroxylase. These results suggest that the activity of the hydroxylase may be regulated by phosphorylation.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D010651:Phenylalanine Hydroxylase / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D011233:Precipitin Tests; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats
chemical_list: D010750:Phosphoproteins; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D010651:Phenylalanine Hydroxylase; D011494:Protein Kinases; D008274:Magnesium