The Chloroplast ATP-Synthase: The Rate of the Catalytic Reaction

Gräber, Peter; Junesch, Ulrike; Thulke, Gerlinda

doi:10.1007/978-94-017-0516-5_39

Cited by 15 publications

(7 citation statements)

References 8 publications

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“…As discussed in a previous paper [6] measurements of the rate of ATP synthesis immediately after generation of the active, reduced enzyme, Eo r*d. are not kineticai!y controlled by a preceding activation process. The curves in Figs.…”

Section: Discussionmentioning

confidence: 93%

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The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H⁺‐ATPase from chloroplasts

Junesch

Gräber

1991

FEBS Letters

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The H+-ATPase from chloroplasts was brought into the active, reduced state. Then, an electrochemica| potential difference of protons across the thylakoid membranes was F_,cnerated b~ ,in acid-base transition, ~lpH, combined with a K*/valinomycin diffusion potential. ~. The initial rate of ATP synthesis was measured with a rapid-mixing quenched-flow apparatus in the time-range between 20-150 ms. The rate of ATP symhesis depends in a sigmoidal way on ,dpH. Increasing diffusion potentials shifts the ApH-dcpendcncies to ~ower ~pH values. Analysis of the data indicate that the rate of ATP synthesss depends on the electrochemical potential diffcrenoe of protons irrespective of the relative contribution of ApH and Ch!oroplast; H~-ATPase; Enzyme-kinetics

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Section: Discussionmentioning

confidence: 93%

“…Here, we measured the initial rate of" ATP synthesis with a rapid-mixing quenchedflow apparatus [5]. Preliminary results were reported in [6].…”

Section: Introductionmentioning

confidence: 99%

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H⁺‐ATPase from chloroplasts

Junesch

Gräber

1991

FEBS Letters

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“…By an imposed gradient by acidbase transition, a valinomycin-induced K + diffusion potential or a combination of both one can be sure that possible local gradients are not higher than the Apn+ between the bulk phases. This method is used by Gr~iber et al [25] to determine H+/ATP in reduced chloroplasts. A stoichiometry of 4.25 was found at the point where the sum of the ATP synthesis and hydrolysis rate is zero (Fig.…”

Section: From Equilibrium Between Apn+ and Phosphate Potentialmentioning

confidence: 99%

The H⁺/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four

et al. 1996

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In this paper the authors emphasise that the proton translocating ATP synthase from thiol-modulated chloroplasts and two cyanobaeterial strains has a coupling ratio of 4 protons per ATP synthesised or hydrolysed. This ratio is determined by several thermodynamic studies at equilibrium between phosphate potential (AGp) and proton gradient (zl/iu+), and is confirmed by measurement of proton flux during ATP hydrolysis. Ratios lower than 4 H+IATP that have been published in the past have predominantly been determined with the oxidised chloroplast enzyme. Errors in these measurements will be discussed.

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“…The results from these measurements can be used to estimate the magnitude of the ApH. The ApH dependency of the rate of ATP hydrolysis catalyzed by the active, reduced enzyme was measured in [16]. About 12% of the maximal rate of ATP hydrolysis was found at a ApH between 3.1 and 3.3.…”

Section: Introduction 2 Materials and Methodsmentioning

confidence: 99%

“…About 12% of the maximal rate of ATP hydrolysis was found at a ApH between 3.1 and 3.3. ApH dependency of the rate of ATP synthesis was measured also in [16,17]. A rate of 200 mM ATP/(M Chl.s), i.e.…”

Section: Introduction 2 Materials and Methodsmentioning

confidence: 99%

Uni‐site catalysis in thylakoids

Fromme

Gräber

1990

FEBS Letters

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ATP-hydrolysis was measured with thylakoid membranes during continuous illumination. The concentrations of free and enzyme-bound ATP, ADP and P, were measured using either cold ATP, [Y-~~P]ATP or P*c]ATP. The concentration of free ATP was constant, free ADP and enxymebound ATP were below the detection limit. Nevertheless, [y-s2P]ATP was bound, hydrolyzed and '*Pi was released. The ADP was not released from the enzyme but cold Pi was bound from the medium, cold ATP was resynthesized and released. A quantitative analysis gave the following rate constants: ATP-binding kATP=2. 101 M-is-', ADP-release: k.,m < IO-*s-i, Pi-release: kn=O.l s-i. These rate constants are considerably smaller than under deenergized conditions. The rate constant for the release of ATP can be estimated to be at least 0.2 s-i under energized conditions. Obviously, energixation of the membrane, i.e. protonation of the enzyme leads mainly to a decrease of the rate of ATP-binding, to an increase of the rate of ATP release and to a decrease of the rate of ADP-release.

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The Chloroplast ATP-Synthase: The Rate of the Catalytic Reaction

Cited by 15 publications

References 8 publications

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H⁺‐ATPase from chloroplasts

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H⁺‐ATPase from chloroplasts

The H⁺/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four

Uni‐site catalysis in thylakoids

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The Chloroplast ATP-Synthase: The Rate of the Catalytic Reaction

Cited by 15 publications

References 8 publications

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H+‐ATPase from chloroplasts

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H+‐ATPase from chloroplasts

The H+/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four

Uni‐site catalysis in thylakoids

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Resources

About

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H⁺‐ATPase from chloroplasts

The rate of ATP‐synthesis as a function of ΔpH and Δψ catalyzed by the active, reduced H⁺‐ATPase from chloroplasts

The H⁺/ATP coupling ratio of the ATP synthase from thiol‐modulated chloroplasts and two cyanobacterial strains is four