Involved in the degradation of 2,4-dinitroanisole (DNAN), an insensitive munition ingredient used in explosive formulations as a replacement for 2,4,6-trinitrotoluene (TNT). Catalyzes the removal of the methyl group from 2,4-dinitroanisole (DNAN) to yield 2,4-dinitrophenol (2,4-DNP) and methanol. 2,4-dinitroanisole + H2O = 2,4-dinitrophenol + H(+) + methanol Binds 2 Zn(2+) ions per subunit. Part of the complex DnhAB composed of the 2,4-dinitroanisole O-demethylase alpha (DnhA) and beta (DnhB) subunits. Constitutively expressed. Unlike other known O-demethylases, it does not require oxygen or electron donors. Belongs to the metallo-beta-lactamase superfamily.