title: Hydrogen peroxide as an alternate substrate for the oxygen-evolving complex.
abstract: Photosystem II reaction centers evolve O2 in the dark when H2O2 is added as a substrate. Although some of this activity can be attributed to catalase, as much as 75% of the activity was not affected by the addition of 1 mM KCN. Several lines of evidence demonstrate that this KCN-insensitive O2 evolution from H2O2 in the dark is catalyzed by the cycling of S states in the oxygen-evolving complex including: inactivation of H2O2-mediated O2 evolution by Ca/EDTA washing; susceptibility of the activity to inhibition by amines like ammonia and Tris; inhibition by CCCP which is known to accelerate the rate of deactivation of the S2 state and; a direct dependence of the rate of O2 evolution on the presence of calcium and chloride.
mesh_terms: D002118:Calcium / Q000494:pharmacology; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D002734:Chlorophyll / Q000378:metabolism*; D004492:Edetic Acid / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism*; D045342:Light-Harvesting Protein Complexes; D008345:Manganese / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins / Q000378:metabolism*; D011190:Potassium Cyanide / Q000494:pharmacology
chemical_list: D002712:Chlorides; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D008345:Manganese; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D004492:Edetic Acid; D006861:Hydrogen Peroxide; D011190:Potassium Cyanide; D010100:Oxygen; D002118:Calcium