Contains FAD. The enzyme catalyses the oxidation of 4-nitrocatechol with the concomitant removal of the nitro group as nitrite. Forms a two-component system with a flavoprotein reductase . The enzymes from the bacteria Lysinibacillus sphaericus JS905 and Rhodococcus sp. strain PN1 were shown to also catalyse EC 18.104.22.168, 4-nitrophenol 2-monooxygenase [1,2] while the enzyme from Pseudomonas sp. WBC-3 was shown to also catalyse EC 22.214.171.124, 4-nitrophenol 4-monooxygenase .