THE WATER-WATER CYCLE IN CHLOROPLASTS: Scavenging of Active Oxygens and Dissipation of Excess Photons

• Kozi Asada

  Department of Biotechnology, Faculty of Engineering, Fukuyama University, Gakuen-cho 1, Fukuyama, 729-0292, Japan;

抄録

▪ Abstract  Photoreduction of dioxygen in photosystem I (PSI) of chloroplasts generates superoxide radicals as the primary product. In intact chloroplasts, the superoxide and the hydrogen peroxide produced via the disproportionation of superoxide are so rapidly scavenged at the site of their generation that the active oxygens do not inactivate the PSI complex, the stromal enzymes, or the scavenging system itself. The overall reaction for scavenging of active oxygens is the photoreduction of dioxygen to water via superoxide and hydrogen peroxide in PSI by the electrons derived from water in PSII, and the water-water cycle is proposed for these sequences. An overview is given of the molecular mechanism of the water-water cycle and microcompartmentalization of the enzymes participating in it. Whenever the water-water cycle operates properly for scavenging of active oxygens in chloroplasts, it also effectively dissipates excess excitation energy under environmental stress. The dual functions of the water-water cycle for protection from photoinihibition are discussed.

収録刊行物

• Annual Review of Plant Physiology and Plant Molecular Biology

  Annual Review of Plant Physiology and Plant Molecular Biology 50 (1), 601-639, 1999-06

  Annual Reviews

キーワード

• General Medicine

詳細情報

• CRID: 1361137045837410048
• NII論文ID: 30022122918
• DOI: 10.1146/annurev.arplant.50.1.601
• ISSN: 10402519
• ISSN: http://id.crossref.org/issn/00664294
• Web Site: https://www.annualreviews.org/doi/pdf/10.1146/annurev.arplant.50.1.601
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