Dehalogenation activity of a miniaturized peroxidase: substrate dependent functional switch

Abstract

Natural peroxidases use 4-halophenols either as substrates in oxidative chemistry or as inhibitors. Herein, we demonstrated that Fe-mimochrome VI*a (Fe-MC6*a), a miniaturized heme-enzyme, is a versatile catalyst as it integrates both these features. We previously reported that Fe-MC6*a catalyzes the chemo- and regio-selective oxidation of 4-halophenols, providing either dehalogenation or oligomerization products, depending on the nature of the halogen atom. In particular, 4-chlorophenol (4-CP) and 4-fluorophenol (4-FP) selectively led to dehalogenation and oligomerization products, respectively. Herein, spin-trapping studies and EPR analysis confirm the ability of Fe-MC6*a into processing halophenols as substrates and provide mechanistic hypothesis for the chemo-divergent reaction outcome. Further, in multiple substrate competition assays, 4-halophenols act as competitive inhibitors of Fe-MC6*a-catalyzed dehalogenation of 2,4,6-trichlorophenol (TCP). Nonetheless, the catalyst retains appreciable turnover in such complex substrate mixtures. Taken together, the combination of substrate-specific selectivity and resilience to the total inhibition position Fe-MC6*a as a promising bioremediation catalyst for simultaneous halophenol detoxification in wastewater-treatment applications.