Monooxygenase that can modify rifampicin, thereby inactivating its antibiotic activity. It constitutes a secondary rifampicin resistance factor. NADPH + O2 + rifampicin = H(+) + H2O + NADP(+) + rifampicin para-naphthoquinone carboxamide NADH + O2 + rifampicin = H(+) + H2O + NAD(+) + rifampicin para-naphthoquinone carboxamide Homodimer. No visible effect on rifampicin resistance.