Arguments are put forward that the active a-oxygen site in the Fe-ZSM-5 catalyst consists of the FeO2+ moiety. It is demonstrated that this zeolite site for FeO2+ indeed obeys the design principles for high reactivity of the FeO2+ moiety proposed earlier: a ligand environment consisting of weak equatorial donors (rather oxygen based than nitrogen based) and very weak or absent trans axial donor. The alpha-oxygen site would then owe its high reactivity to the same electronic structure features that lends FeO2+ its high activity in biological systems, as well as in the classical Fenton chemistry.