Intact spinach chloroplasts isolated by the modified silica sol density centrifugation scavenged H2O2on illumination at a rate about 3-fold that of bicarbonate-dependent O2-evolution. Accompanying the disappearance of 1 mole of H2O2is the evolution of a half mole of O2. The photoscavenging of H2O2was inhibited by 3(3,4-dichloro-phenyl)-l, l-dimethylurea, cyanide and azide. These results indicate that in chloroplasts H2O2is reduced to H2O by a cyanide and azide-sensitive peroxidase using a photoreductant as an electron donor.
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