Catalyzes the oxidation of either pyridoxine 5'-phosphate (PNP) or pyridoxamine 5'-phosphate (PMP) into pyridoxal 5'-phosphate (PLP). Involved in the PLP salvage pathway. Has a higher preference for PNP over PMP. May also catalyze the epimerization of the S- and R-forms of NAD(P)HX, a damaged form of NAD(P)H that is a result of enzymatic or heat-dependent hydration. This is a prerequisite for the S-specific NAD(P)H-hydrate dehydratase to allow the repair of both epimers of NAD(P)HX. H2O + O2 + pyridoxamine 5'-phosphate = H2O2 + NH4(+) + pyridoxal 5'-phosphate O2 + pyridoxine 5'-phosphate = H2O2 + pyridoxal 5'-phosphate (6R)-NADHX = (6S)-NADHX (6R)-NADPHX = (6S)-NADPHX Binds 1 FMN per subunit. Binds 1 potassium ion per subunit. Cofactor metabolism; pyridoxal 5'-phosphate salvage; pyridoxal 5'-phosphate from pyridoxamine 5'-phosphate: step 1/1. Cofactor metabolism; pyridoxal 5'-phosphate salvage; pyridoxal 5'-phosphate from pyridoxine 5'-phosphate: step 1/1. Homodimer. Expressed in leaves, stems, flowers and roots. Circadian regulation. Up-regulated by light, heat, jasmonic acid, ethylene and abscisic acid treatments. Down-regulated by drought and salt treatment. Not induced by UV irradiation. Most plant PPOX proteins have both a pyridoxamine 5'-phosphate oxidase domain and an extra YjeF N-terminal domain. Mutants with reduced expression of PPOX1 (RNAi) have lower levels of total B6 vitamers, a reduced growth and are sensitive to high light. Not detected in roots. In the N-terminal section; belongs to the NnrE/AIBP family. In the C-terminal section; belongs to the pyridoxamine 5'-phosphate oxidase family. Truncated N-terminus. Truncated N-terminus.