Driving Force for Oxygen-Atom Transfer by Heme-Thiolate Enzymes

摘要

The heme-thiolate peroxygenase from Agrocybe aegerita (AaeAPO, EC 1.11.2.1) is a versatile biocatalyst and cytochrome P450 analogue which catalyzes a variety of oxygenation reactions with high efficiency and selectivity. Our recent kinetic characterization of AaeAPO-catalyzed reactions has shown that AaeAPO compound I is an oxo-Fe~(IV) porphyrin radical cation. The reactivity of AaeAPO-I toward a panel of substrates showed very fast C—H hydrox-ylation rates, similar to those of cytochrome P450 (CYP119-I), and much faster than chloroperoxidase compound I (CPO-I). Mechanistic probes have revealed a large hydrogen isotope effect for aliphatic C—H hydroxylation and rearranged products from the hydroxylation of norcarane. There is, however, very little information available regarding the thermodynamic properties of such highly reactive oxo-Fe species for any heme-thiolate proteins.