[Properties of the halide complexes of horseradish peroxidase in the presence of aromatic substrates].

The fluoride, chloride and bromide complexes of horseradish peroxidase were investigated by optical methods, NMR and ESR. The galide binding may be increased or reduced by means of enzyme-substrate complex formation of horseradish peroxidase with aromatic donors. Both sign and magnitude of the effect depends on galide ligand properties and structure of the donor's molecule. The maximum of the galide complex optical density removes redwise with the galide weight increasing. Cloride and bromide binding leads to the appreciable decrease of the high-spin portion in ferriheme spin equilibrium. The cloride complex of horseradish peroxidase demonstrates a low symmetry of the ligand field, in comparison of the fluoride complex.