Reactions of superoxide dismutases with HS−/H2S and superoxide radical anion: An in vitro EPR study

• FeSOD from E. coli and P. leiognathi are resistant to HS−/H2S-induced reduction.
• HS−/H2S appears to provoke a release of manganese from MnSOD.
• HS−/H2S reduced Cu2+ to Cu1+ in CuZnSOD.
• 5 d-electron systems predominate in MnSOD and FeSOD.

Interactions of hydrogen sulfide (HS−/H2S), a reducing signaling species, with superoxide dimutases (SOD) are poorly understood. We applied low-T EPR spectroscopy to examine the effects of HS−/H2S and superoxide radical anion (O2·−)(O2·−) on metallocenters of FeSOD, MnSOD, and CuZnSOD. HS−/H2S did not affect FeSOD, whereas active centers of MnSOD and CuZnSOD were open to this agent. Cu2+ was reduced to Cu1+, while manganese appears to be released from MnSOD active center. Untreated and O2·−O2·− treated FeSOD and MnSOD predominantly show 5 d-electron systems, i.e. Fe3+ and Mn2+. Our study provides new details on the mechanisms of (patho)physiological effects of HS−/H2S.