• 2011 ). On the other side, plants have developed some enzymatic systems including superoxide dismutases (SOD), catalases (CAT), ascorbate peroxidases (APX), peroxiredoxins and non-enzymatic mechanisms to protect against oxidative damage caused by these ROS (Agrawal et al. (springeropen.com)
  • Fe3+ + H2O + oxidized substrate In this mechanism, the enzyme reacts with one equivalent of H2O2 to give [Fe4+=O]R' (compound I). This is a two-electron oxidation/reduction reaction in which H2O2 is reduced to water, and the enzyme is oxidized. (wikipedia.org)
  • The initial step for both catalytic processes is the heterolytic reduction of H2O2 to H2O, giving rise to a two-electron oxidation of the ferric enzyme to a ferryl-porphyrin π cation radical intermediate, compound I (i.e. (auburn.edu)
  • To complete the catalase reaction, compound I returns to the ferric state by oxidation of another H2O2 to form O2 and H2O. (auburn.edu)
  • However, the peroxidase reaction is completed by the subsequent reduction of compound I to compound II (i.e. (auburn.edu)
  • Conversely, catalase activity can sustain high concentrations of H2O2 without the enzyme inactivation. (auburn.edu)
  • Based on this mechanism, both activities should be mutually antagonistic and peroxidatic electron donors should inhibit the catalase activity. (auburn.edu)
  • Clearly, the catalase mechanism and the interrelationship between the catalase and peroxidase functions of KatG are much more complex than has been previously appreciated, and pH plays an important factor in both activities. (auburn.edu)
  • One oxidizing equivalent resides on iron, giving the oxyferryl intermediate, and in many peroxidases the porphyrin (R) is oxidized to the porphyrin pi-cation radical (R'). Compound I then oxidizes an organic substrate to give a substrate radical and Compound II, which can then oxidize a second substrate molecule. (wikipedia.org)
  • intermediate dominated during electron donor-stimulated catalase activity of MtKatG, and this intermediate converted directly to the ferric state upon depletion of H2O2. (auburn.edu)
  • Catalase activity is optimal near neutral pH (i.e., pH ~ 7.5), whereas peroxidase activity is optimal under acidic conditions (i.e., pH ~ 4.5) and requires an exogenous electron donor. (auburn.edu)