 The active ferric center is coordinated by four protein ligands—two histidine and two tyrosinate residues—in a trigonal bipyramidal manner with a water molecule occupying the fifth coordination site.Once a catecholate substrate binds to the metal center in a bidentate fashion through the deprotonated hydroxyl groups, the ferric iron “activates” the substrate by means of abstracting an electron to produce a radical on the substrate.This then allows for reaction with dioxygen and subsequent intradiol cleavage to occur through a cyclic anhydride intermediate.