Microperoxidase-8 Associated to CTAB Micelles: A New Catalyst with Peroxidase Activity

Abstract

Literature data have pointed to microperoxidase-8 (MP-8) as an attractive water-soluble model for studying the reaction mechanism of peroxidases because this heme peptide is able to form the same enzyme intermediates during reaction with peroxides. In this work, we have demonstrated that the association of Fe(III)MP-8 with CTAB micelles provides a microenvironment with an alkaline interface and a hydrophobic core that gives special characteristics to the Fe(III)MP-8/peroxide (tert-butyl hydroperoxide or hydrogen peroxide) reaction as compared with homogeneous medium. EPR spin-trapping studies using 5,5-dimethyl-1-pyrroline N-oxide and computer simulations of the experimental spectra were performed to determine the reaction mechanism. From the analysis of the results, alkoxyl and hydroxyl radicals of t-BuOOH and HOOH, respectively, were identified as the initial radicals produced, presumably by homolytic scission of the O−O bond by Fe(III)MP-8/CTAB. The UV−vis spectral changes for Fe(III)MP-8 pointed to th...