Fig. 22.

Proposed catalytic pathway of QDOs, consolidated from the mechanistic scenarios suggested for the Mn(II)/Fe(II) enzyme [115] and the Cu(II) enzyme [117]. Two alternative cleavage mechanisms, a nucleophilic ring formation (red, pathway 1) and a Criegee rearrangement (green, pathway 2) are depicted. (The alternative redox-independent dioxygen reduction mechanism, which proceeds via peroxidate formation in one step, is not shown.). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)