Further Characterization of a Novel L-Phenylalanine Oxidase (Deaminating and Decarboxylating) from Pseudomonas sp. P-501

L-Phenylalanine oxidase, purified to homogeneity from Pseudomonas sp. P-501, had a molecular weight of about 140,000 and consisted of two subunits identical in molecular weight (about 68,000). The sedimentation coefficient ( $S20,w0$ ) of the enzyme was determined to be 8.18S by ultracentrifugation. The enzyme showed absorption maxima at 276, 390, and 466 nm and a shoulder around 490 nm and contained 2 mol of FAD per mol of enzyme. Oxygen-18 supplied as molecular oxygen was incorporated into the carbonyl group of α-phenylacetamide formed by the enzymic oxidation of L-phenylalanine. Michaelis constants of the enzyme were 1.07 × 10 ^-2 mM for L-phenylalanine and 1.82 mM for oxygen. Maximum activities in oxidation and oxygenation (catalyzed simultaneously by the enzyme) were observed at different pHs and different temperatures. Several metal ions inhibited the oxidase activity preferentially.