CATALYTIC INTERMEDIATES IN THE REACTION OF DEUTEROFERRIHEME WITH M-CHLOROPEROXYBENZOIC ACID

Deuteroferriheme (DFH) reacts with m-chloroperoxybenzoic acid (m-CPBA) to produce a reaction intermediate whose optical spectrum resembles t hat of horseradish peroxidase (HRP) compound 0. To exclude problems re lated to aggregation, the fraction of dimers was maintained below 2%. Under these conditions, the reaction of DFH with m-CPB in 10 mM phosph ate containing 1% v/v 1,2-dimethoxyethane (I = 0.1M NaCl) at pH 5.5 at 1 degrees C was shown to produce an intermediate that has a distincti ve Soret band near 350 nm, in agreement with earlier observations in t he literature. The EPR spectrum of this intermediate indicates that it contains half ferric iron and cannot be a ferryl dimer. Its structure is more consistent with that of a ferric, ferryl dimer and a scheme s upporting its formation has been proposed.