Involved in the biodegradation of chlorinated nitroaromatic compounds. Catalyzes the reduction of 4-chloronitrobenzene to yield 1-hydroxylamino-4-chlorobenzene. Probably also able to catalyze the two-electron reduction of nitrobenzene (NB) to produce a nitrosobenzene (NOB) intermediate, which is immediately reduced to hydroxylaminobenzene (HAB) by a second two-electron transfer. H2O + N-phenylhydroxylamine + 2 NADP(+) = 2 H(+) + 2 NADPH + nitrobenzene Binds 1 FMN per subunit. Xenobiotic degradation; nitrobenzene degradation. Xenobiotic degradation; 4-chloronitrobenzene degradation. Belongs to the nitroreductase family.