 This "K. oxytoca" enzyme represents a unique example whereby the metal ion present dictates which reaction is catalyzed.The quercetinases and ARD enzymes all are members of the cupin superfamily, to which the mononuclear iron enzymes also belong.The metal coordination scheme for the QueD enzymes is either a 3-His or 3-His-1-Glu with the exact arrangement being organism-specific.