Partial purification of phenylalanine hydroxylase from dog liver

Phenylalanine hydroxylase from dog liver was purified ten fold. The physical and kinetic properties of phenylalanine hydroxylase from dog liver in many respects closely resemble physical and kinetic properties of the same enzyme from other organism reported in the literature. The Km value determined for phenylalanine hydroxylase from dog liver for phenylalanine is 3.7 [plus-minus] 1.1 mN; for 6,7-dimethyltetrahydropterin is 0.17 [plus-minus] 0.10 mM; and for tetrahydrobiopterin is 0.34 [plus-minus] 0.03 mH. A new assay developed in this study is especially suited for detection of phenylalanine hydroxylase from dog liver and it makes possible the detection of enzyme activity at low concentration of enzyme.