Catalyzes the oxidation of alkyl nitronates to produce the corresponding carbonyl compounds and nitrites. Anionic forms of nitroalkanes are much better substrates than are neutral forms. ethylnitronate + O2 = acetaldehyde + chemical entity + H(+) + nitrite Binds 1 FMN per subunit. Homodimer. Belongs to the nitronate monooxygenase family. NMO class II subfamily.