Toxoflavin lyase (TflA) is metalloenzyme degrading toxoflavin at the presence of oxygen, Mn(II), and dithiothreitol. TflA is structurally homologous to proteins of the vicinal oxygen chelate superfamily. The structure of TflA contains fold that displays a rare rearrangement of the structural modules indicative of domain permutation. Moreover, unlike the 2-His-1-carboxylate facial triad commonly utilized by vicinal oxygen chelate dioxygenases and other dioxygen-activating non-heme Fe(II) enzymes, the metal center in TflA consists of a 1-His-2-carboxylate facial triad. Toxoflavin is an azapteridine that is toxic to various plants, fungi, animals, and bacteria.