Mesoferriheme regeneration from its hemoprotein enzyme compound I analog: absorption and kinetic properties of one- and two-electron oxidation products

Abstract Spectral and kinetic data obtained in studies of the biphasic in situ regeneration of mesoferriheme (mfh) from oxidized species formed through the NaOCl oxidation of heme are utilized to calculate extinction coefficients of dinuclear iron species which have been proposed as models of peroxidase Compounds I and II (A and B below). For the proposed regeneration mechanism, involving consecutive one-electron redox processes, the calculated values of ϵ A and ϵ B are 4x10 4 and 5x10 4 M −1 cm −1 , respectively. These values are somewhat greater than those previously calculated for analogous derivatives of deuteroferriheme. Both k 1 and k 2 are independent of pH over the range 6.9–9.1 and of total phosphate buffer concentration from 8 to 50 mM at pH 6.9 suggesting that, under these conditions, there is an absence of significant dissociation of the proposed dinuclear iron species.