Catalyzes the oxidation of F420H(2) with O(2) (By similarity). May be involved in O(2) detoxification, reducing the intracellular O(2) concentration to a level allowing growth at the expense of methane formation (By similarity). O2 + 2 reduced coenzyme F420-(gamma-L-Glu)(n) = 2 H(+) + 2 H2O + 2 oxidized coenzyme F420-(gamma-L-Glu)(n) Binds 1 FMN per subunit. Binds 2 iron ions per subunit. By iron limitation. In the N-terminal section; belongs to the zinc metallo-hydrolase group 3 family. Was originally thought to be a subunit of methylviologen hydrolase II.