Photoinduced Production of Hydrogen Peroxide at the Acceptor Side of Photosystem II

O. M. Zastrizhnaya,^1,2 A. A. Khorobrykh,¹ M. S. Khristin,¹ and V. V. Klimov¹

¹Institute of Soil Science and Photosynthesis, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia; fax: (80967) 79-05-32; E-mail: khor@issp.serpukhov.su

²To whom correspondence should be addressed.

Submitted March 18, 1996; revision submitted December 3, 1996.

Photoinduced production of H₂O₂ was studied in subchloroplast oxygen-evolving photosystem II (PS II) particles and isolated complexes of PS II reaction centers using luminol-peroxidase chemiluminescence and pulse photoactivation. The photoinduced production of H₂O₂ in subchloroplast PS II particles is suppressed by inhibitors of electron transfer between the primary (Q_A) and secondary (Q_B) quinone acceptors of PS II (3-(3,4-dichlorophenyl)-1,1-dimethyl urea, o-phenanthroline) or scavengers of ***O₂^- (nitroblue tetrazolium or cytochrome c). The rate of photoinduced production of H₂O₂ in subchloroplast PS II particles depends on pH and is maximal at pH 8.5 (4.5 µmoles H₂O₂/mg Chl per hour). The photoinduced production of H₂O₂ in isolated reaction center complexes is 0.1 H₂O₂ molecule per reaction center per saturating flash. This reaction is suppressed by K-15, an inhibitor of electron transfer in PS II, which accelerates the charge recombination in the ion-radical pair [P680⁺ Pheo^-]. The photoinduced production of H₂O₂ at the acceptor side of PS II is a result of the interaction between molecular oxygen and reduced electron acceptors of PS II (pheophytin and plastoquinone Q_B).

KEY WORDS: photosynthesis, photosystem II, hydrogen peroxide.

---