Nitronate monooxygenase that uses molecular oxygen to catalyze the oxidative denitrification of alkyl nitronates. Acts on propionate 3-nitronate (P3N), the presumed physiological substrate. Is likely involved in the degradation of P3N, that allows Pseudomonas sp. JS189 to grow on 3-nitropropionate/P3N as the sole source of nitrogen, carbon, and energy (PubMed:20382807). Also probably functions in the detoxification of P3N, a metabolic poison produced by plants and fungi as a defense mechanism (By similarity). Is not active against 3-nitropropionate, nor with neutral or nitronate forms of 1-nitropropane, 2-nitropropane, nitroethane, nitromethane, 1-nitropentane, and 2-nitroethanol (PubMed:20382807). H2O + 3 O2 + 3 propionate 3-nitronate = 3 3-oxopropanoate + 3 H(+) + H2O2 + 2 nitrate + nitrite Binds 1 FMN per subunit. Constitutively expressed. At physiological pH, 3-nitropropionate (3-NPA) exists in equilibrium with its conjugate base, propionate-3-nitronate (P3N). P3N is a potent irreversible inhibitor of the key enzyme succinate dehydrogenase in the Krebs cycle and electron transport chain. P3N has been shown to be a toxic metabolite to bacteria, plants, fungi, mammals or any organism that uses succinate dehydrogenase. Belongs to the nitronate monooxygenase family. NMO class I subfamily.