Effect of Preillumination of Spinach Leaves on the Coupling Efficiency of Chloroplasts

Ji, Wei; Shen, Yu‐Mei; Li, D. Y.; Dai, Hwa

doi:10.1007/978-94-017-0516-5_8

Cited by 1 publication

(1 citation statement)

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“…P/O ratio might be increased by preillumination of leaves or treatment of thylakoids with a number of chemicals, such as aureomycin, polymyxin, 6-benzylaminopurine (an analogue of cytokinin), polybasic acids and high concentration of inorganic phosphate, which were called coupling efficiency improvers (Feng and Shen 1983;Huang et al 1982;Huang and Shen 1988;Huang and Wei 1984;Shen 1990;Wei et al 1987Wei et al , 1990. These chemicals might act as allosteric effectors on different subunits of CF~ to induce the conformational changes of CF1, which probably decreased the ineffective proton leakage through H+-ATP synthase and promoted ATP synthesis during photophosphorylation.…”

Section: Introductionmentioning

confidence: 99%

Malate regulation of Mg2+-ATPase of chloroplast coupling factor 1

Ren

Shen

1995

Photosynth Res

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The regulatory effects of malate on chloroplast Mg(2+)-ATPase were investigated and the mechanism was discussed. Malate stimulated methanol-activated membrane-bound and isolated CF1 Mg(2+)-ATPase activity. The γ subunit of CF1 may be involved in malate regulation of the enzyme function. Modification of γ subunit at one site of the peptide by NEM may affect malate stimulation of ATPase while at another site may have no effect. The effect of malate on the Mg(2+)-ATPase was also controlled by the Mg(2+)/ATP ratio in the reaction medium. The enhancing effect of malate on Mg(2+)-ATPase activity depended on the presence of high concentrations of Mg(2+) in the reaction mixture. Kinetic study showed that malate raised the Vmax of catalysis without affecting the Km for Mg(2+) ATP. The experiments imply that the stimulation of Mg(2+)-ATPase by malate is probably correlated with the Pi binding site on the enzyme. The regulation of ATPase activity by malate in chloroplasts may be relevant to its function in vivo.

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Section: Introductionmentioning

confidence: 99%