Spinach chloroplasts scavenge hydrogen peroxide on illumination

Intact spinach chloroplasts isolated by the modified silicasol density centrifugation scavenged H₂O₂ on illumination ata rate about 3-fold that of bicarbonate-dependent O₂-evolution.Accompanying the disappearance of 1 mole of H₂O₂ is the evolutionof a half mole of O₂. The photoscavenging of H₂O₂ was inhibitedby 3(3,4-dichloro-phenyl)-l, l-dimethylurea, cyanide and azide.These results indicate that in chloroplasts H₂O₂ is reducedto H₂O by a cyanide and azide-sensitive peroxidase using a photoreductantas an electron donor. (Received July 4, 1980; )