β-Naphthyl oligophosphates : Inhibitors of photophosphorylation and H^+-ATPase of spinach chloroplasts

概要

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β-Naphthyl di-, tri- or tetraphosphate inhibits photophosphorylation of spinach chloroplasts competitively with ADP, whereas β-naphthyl monophosphate inhibits it competitively with Pi. The apparent Ki of β-naphthyl diphosphate for the ADP site was 300 μM and that of β-naphthyl monophosphate for the Pi site was 1.45 mM. At 10 mM, both of these two organic phosphates inhibited photophosphorylation more than 90%. None of the above four β-naphthyl phosphates were phosphorylated by chloroplasts. β-naphthyl di-, tri- or tetraphosphate inhibits ATPase activity of isolated chloroplast coupling factor 1 (CF_1) (EC 3.6.1.3) and light-triggered ATPase activity of chloroplasts competitively with ATP, whereas β-naphthyl monophosphate acts non-competitively. None of the four β-naphthyl phosphates were hydrolyzed by these two ATPase activities. At concentrations equal to ADP or ATP, β-naphthyl di-, tri- or tetraphosphate inhibited these three reactions in the order; ATPase of isolated CF_1 > photophosphorylation > light-triggered ATPase of chloroplasts. The results suggest that the effect of the monophosphate is principally on the Pi site(s) and that of the di-, tri- or tetraphosphate is on the adenine nucleotide site(s) on the active center of CF_1.
日本植物生理学会の論文