A Kinetic study of the pH dependence of the reaction between metmyoglobin and para-nitroperoxybenzoic acid
MetadataShow full item record
The reaction between metmyoglobin and para-nitroperoxybenzoic acid was studied at 0.1 M ionic strength and the apparent bimolecular rate constants were determined between pH 5.0 and 11.0. The reaction was found to be influenced by enzyme as well as substrate ionizations. Contrary to the general belief that metmyoglobin preferentially reacts with the ionized substrate, the results of this study indicate that it is the unionized substrate which is preferred. The maximal rates for the formation of Mb(IV) from the reaction of metmyoglobin and para-nitroperoxybenzoic acid were found to be higher than that for the formation of Mb(IV) from hydrogen peroxide. A model has been proposed to explain the results in which hydrogen bond formation occurs between the distal histidine and one oxygen of the substrate, facilitating O-O bond cleavage.