Hydrogen Peroxide and Superoxide Anion Radical Photoproduction in PSII Preparations at Various Modifications of the Water-Oxidizing Complex

• Main Author: Andrey Khorobrykh
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Plants
• Subjects: photosystem II; water-oxidizing complex; cytochrome b559 superoxide anion radical; hydrogen peroxide
• Online Access: https://www.mdpi.com/2223-7747/8/9/329
• ISSN: 2223-7747

The photoproduction of superoxide anion radical (O₂^{&#8722;&#8226;}) and hydrogen peroxide (H₂O₂) in photosystem II (PSII) preparations depending on the damage to the water-oxidizing complex (WOC) was investigated. The light-induced formation of O₂^{&#8722;&#8226;} and H₂O₂ in the PSII preparations rose with the increased destruction of the WOC. The photoproduction of superoxide both in the PSII preparations holding intact WOC and the samples with damage to the WOC was approximately two times higher than H₂O₂. The rise of O₂^{&#8722;&#8226;} and H₂O₂ photoproduction in the PSII preparations in the course of the disassembly of the WOC correlated with the increase in the fraction of the low-potential (LP) Cyt <i>b</i>₅₅₉. The restoration of electron flow in the Mn-depleted PSII preparations by exogenous electron donors (diphenylcarbazide, Mn²⁺) suppressed the light-induced formation of O₂^{&#8722;&#8226;} and H₂O₂. The decrease of O₂^{&#8722;&#8226;} and H₂O₂ photoproduction upon the restoration of electron transport in the Mn-depleted PSII preparations could be due to the re-conversion of the LP Cyt <i>b</i>₅₅₉ into higher potential forms. It is supposed that the conversion of the high potential Cyt <i>b</i>₅₅₉ into its LP form upon damage to the WOC leads to the increase of photoproduction of O₂^{&#8722;&#8226;} and H₂O₂ in PSII.