Über den mechanismus der katalase-wasserstoffperoxid-reaktion II. Die aktivitätszentren der katalase und ihre wirkungs-weise

• 1.

  1. Besides the prosthetic groups, disulfide, sulfhydryl and basic groups in the protein component of catalase are active centers for the reaction with H₂O₂. The disulfide and sulfhydryl groups behave as a redox system acting upon H₂O₂. The basic groups interact with the prosthetic groups. This influences the binding strength of the peroxide, which is combined with the Fe⁺ of the prosthetic group. It is discussed which groups in the protein component could be responsible for the heme-protein interaction.

• 2.

  2. The actual activity of catalase may be derived from the measured activity-pH relationship by elimination of the five intermediate equilibria. These are: the dissociation of peroxide, the dissociation of catalase hydroxide, the dissociation of catalase peroxide, the pH dependence of the redox potential and the pH dependence of latent sulfhydryl groups. The actual catalase activity is pH dependent because of heme-protein interaction.

• 3.

  3. With the help of these results the fundamental mechanism of the catalatic reaction may be explained. The oxidation of peroxide to oxygen by the disulfide bridges of catalase is the rate-determining process, the peroxide being combined with the Fe of the heme group. The reaction velocity depends upon the size of the catalase redox potential and the strength of the heme-protein interaction. Values for the magnitude of these quantities are presented