Weak Light-Induced Oxygen Consumption Observed during Photoreactivation Is Coupled to the Recovery of Oxygen Evolving Activity

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During photoreactivation of the O_2-evolving center in Tris-inactivated/Mn-depleted thylakoids, a slow O_2-consumption occurred. This O_2-consumption became detectable when the O_2-evolving activity of thylakoids was inactivated by Tris-treatment and decreased as photoreactivation proceeded. The O_2-consumption and photoreactivation similarly required Mn^<2+> at μM levels in addition to PSII electron donors and shared several common characteristics. Stimulation of O_2-consumption and photoreactivation by these cofactors were always accompanied by enhancement in chlorophyll fluorescence induction, suggesting the involvement of a Mehler-type reaction in photoreactivation. Although the electron transport due to this O_2-consumption was rapid enough to oxidize 4 Mn^<2+> ions to reconstitute the tetranuclear Mn-cluster in each O_2-evolving center in a few seconds, actual recovery of O_2-evolving activity occurred more slowly in a few minutes. It was infer-red that photoreactivation in Tris-inactivated thylakoids is not a simple photooxidation of Mn^<2+> but involves more complicated processes which are coupled to the Mehler-type electron transport from PSII to oxygen via PSI.
日本植物生理学会の論文