title: Phenylalanine hydroxylase. Evidence that the enzyme from human liver might not be a phosphoprotein.
abstract: Phenylalanine hydroxylase from fresh human liver was purified to homogeneity with a 60% yield by a three steps procedure involving hydrophobic chromatography on Phenyl-Sepharose, ion exchange chromatography on DEAE-Cellulose and High Performance gel permeation chromatography. The purified native enzyme had an estimated molecular weight of 165,000. It gave a single band on Sodium Dodecylsulfate polyacrylamide gel electrophoresis under an estimated molecular weight of 55,000. Neither the purified human enzyme, nor that present in a liver extract could be activated under phosphorylating conditions. Moreover, the purified human liver phenylalanine hydroxylase was found to be devoid of protein-bound phosphate and no phosphate could be incorporated from [32P]-ATP in the presence of cyclic-AMP - dependent protein kinase. These data suggest that phenylalanine hydroxylase from human liver, unlike that of rat liver, might not be a phosphoprotein.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D010651:Phenylalanine Hydroxylase / Q000302:isolation & purification* / Q000378:metabolism; D010750:Phosphoproteins / Q000302:isolation & purification; D010766:Phosphorylation
chemical_list: D000596:Amino Acids; D010750:Phosphoproteins; D010651:Phenylalanine Hydroxylase