Effects of chloride ion on HILL reactions in Euglena chloroplasts

概要

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Effects of Cl^- and other anions on the rate of HILL reaction in Euglena chloroplasts were investigated. Cl^- accelerated the reaction rate with ferricyanide as HILL oxidant; Br^-, F^- and I^- were also effective; NO_3^-, PO_4^<2-> and SO_4^<2-> were less effective. Divalent cations, Ca^<2+> and Mg^<2+>, were also highly effective. The promoting effects of these ions were highly dependent on pH and the nature and concentration of the HILL oxidant used. Accelerating effects of the ion increased with decreasing concentrations of ferricyanide. Generally, the stimulating effect of Cl^- was much more marked at pH 7-7.5, with little effect at pH 5. Thus, the pH-activity relationship in the HILL reaction is more or less markedly modified by addition of ions. Cl^-, and other anions, accelerated the reaction by affecting only the dark rate-limiting portion of the HILL reaction; the light reaction constant remained uninfluenced. We inferred that some reaction step, at which ferricyanide receives electron from photo-system 2, is accelerated by Cl^- and other ions. Cl^- effects were rather small, or undetectable, with DPIP or p-benzoquinone as oxidants.
日本植物生理学会の論文