Spinach chloroplasts scavenge hydrogen peroxide on illumination

Abstract

Intact spinach chloroplasts isolated by the modified silica sol density centrifugation scavenged H₂O₂ on illumination at a rate about 3-fold that of bicarbonate-dependent O₂-evolution. Accompanying the disappearance of 1 mole of H₂O₂ is the evolution of a half mole of O₂. The photoscavenging of H₂O₂ was inhibited by 3(3,4-dichloro-phenyl)-l, l-dimethylurea, cyanide and azide. These results indicate that in chloroplasts H₂O₂ is reduced to H₂O by a cyanide and azide-sensitive peroxidase using a photoreductant as an electron donor.