Hydroperoxidase activities of ferrihemes: heme analogues of peroxidase enzyme intermediates.

By reaction of deuteroferriheme (DFH) with peroxo acids, spectroscopically distinct and peroxidatically active deuteroferriheme-peroxide compounds (DPC) are formed. These species closely resemble, and are probably identical with, the species formed by reaction of DFH with H2O2, which has previously been considered to be an analogue of peroxidase compound I. Stopped-flow spectrophotometric titration studies imply: (a) that DPC is formed by reaction of 1.9 +/- 0.2 mol of DFH with 1 mol of peroxo acid; (b) that the spectral change accompanying formation of DPC is independent of the peroxo acid oxidant used. Titration of the oxidizing power of DPC formed with H2O2 implies that submaximal yields of DPC are obtained, a result that could implicate DPC species as analogues of catalase compound I in the catalase action of ferrihemes. Preliminary results suggest that DPC may involve both monomeric and dimeric heme components.