Non-heme-dependent dioxygenase that catalyzes the oxidative epoxidation of (S)-2-hydroxypropylphosphonate into (1R,2S)-epoxypropylphosphonate, the final step in the biosynthesis of fosfomycin antibiotic. (S)-2-hydroxypropylphosphonate + H2O2 = (1R,2S)-epoxypropylphosphonate + 2 H2O Binds 1 Fe(2+) ion per subunit. Antibiotic biosynthesis; fosfomycin biosynthesis. Homotrimer. Belongs to the non-heme iron-dependent dioxygenase family.