A methylene dioxy group in aromatic compounds is subject to O-dealkylation (e.g., 3,4-methylenedioxyampheta-mine (53)78) (eqn [18]). The process generates formic acid and the catechol metabolite 54 as final products. However, in the course of the reaction a portion of the enzyme can be inactivated by formation of what has been termed a metabolic intermediate (MI) complex79,80 characterized by an absorption peak maximum at 455 nm in the difference spectrum of reduced cytochrome P450. The complexing species is believed to be a carbene that associates with heme Fe2 + (55), in much the same way that carbon monoxide81,82 does. The complex is of moderate stability, and thus a quasi-irreversible inhibitor of the enzyme. It ultimately dissociates to generate ferric cytochrome P450, carbon monoxide, and the catechol 54.83


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