Catalyzes the 6-electron oxidation of protoporphyrinogen-IX to form protoporphyrin-IX. 3 O2 + protoporphyrinogen IX = 3 H2O2 + protoporphyrin IX Binds 1 FAD per subunit. Porphyrin-containing compound metabolism; protoporphyrin-IX biosynthesis; protoporphyrin-IX from protoporphyrinogen-IX: step 1/1. Porphyrin-containing compound metabolism; chlorophyll biosynthesis. Homodimer. Expressed in expanding premature leaves. Decreased expression in oldest leaves. Expressed at very low level in roots. Oscillating expression during diurnal growth. Maximal expression in the dark period. Belongs to the protoporphyrinogen/coproporphyrinogen oxidase family. Protoporphyrinogen oxidase subfamily.