Evidence for the presence of Mn(II) in a peanut peroxidase. An EPR study

The characteristics of the paramagnetic centers of the main cationic isozyme of peanut peroxidase are analyzed using electron paramagnetic resonance. Two main paramagnetic species have been detected. The EPR spectrum of the native cationic peanut peroxidase shows features which correspond to those of high spin ferric heme iron. A second paramagnetic center has been identified as manganese (Mn2+). The EPR spectra of the reduced enzyme and its fluoride, cyano, carbon monoxide, thiolate and hydroxy derivatives have been studied. The signal attributed to Mn(II) disappeared after dialysis against 50 mM EDTA, which removed the Mn ions, as it was confirmed by atomic absorption spectroscopy. The disappearance of the Mn signal after the formation of the cyano, thiolate and hydroxy complexes suggest a transfer of electrons from the Mn(II) ions. The significance of manganese in the catalytic cycle of cationic peanut peroxidase discussed.