Free-energy changes of the glutaminase reaction and the hydrolysis of the terminal pyrophosphate bond of adenosine triphosphate

Benzinger, T. H.; Kitzinger, C.; Hems, R.; Burton, K.

doi:10.1042/bj0710400

Cited by 104 publications

(32 citation statements)

References 19 publications

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“…The "threshold" ApH levels under which no phosphorylation was observed varied with the pH during the phosphorylation stage. This seems to be in good agreement with the increase in the free energy of ATP synthesis with increase of pH [34]. These "threshold)' levels were previously shown to be detectable also during steady-state phosphorylation in chloroplasts (Pick, Rottenberg end Avron, unpublished results) and were reported also for mitochondria, where the minimum K+ concentration gradient supporting ATP synthesis was 40mV [6] and also, when the proton electrochemical gradient was changed by changing the K+ concentration in valinomycintreated mitochondria, no ATP synthesis was detected below a gradient of 40 mV (although in this case the hexokinase-glucose trap was used) [5].…”

Section: Stimulation Of Postillumination a T P Synthesis By A Diffusupporting

confidence: 75%

Stimulation of ATP Synthesis by a Membrane Potential in Chloroplasts

Schuldiner

Rottenberg

Avron

1973

European Journal of Biochemistry

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Chloroplasts preloaded with protons by light-induced proton uptake do not synthesize ATP in a following dark period if the proton concentration gradient (ApH) is lower than 2.5-3.0 pH units. At such suboptimal ApH values synthesis of ATP can be obtained by imposing a diffusion potential across the chloroplast membrane. This potential was realized by providing a high external concentration of either KC1 in the presence of valinomycin or of NaCl in the presence of monactin. Diffusion-potential-induced stimulation of ATP synthesis was observed both in chloroplasts and in bacterial chromatophores.The stimulation could be abolished by the addition of a highly permeant anion, like picrate.It is proposed that the effect of the diffusion potential indicates that an increase in the electrochemical gradient of protons can be coupled to the synthesis of ATP.ATP synthesis coupled to the flow of cations down their gradients has been demonstrated in several systems that contain an ATP-driven ion pump. In erythrocytes high external sodium concentration together with high internal potassium induced ATP synthesis by the reversal of the Na+-Kf pump In chloroplasts proton gradients generate high yields of ATP provided the chloroplasts are loaded with a sufficient number of protons and the pH gradient is large. These requirements are met both in acid-base transition or in post illumination-type experiments [13]. In both cases it can be assumed that proton concentration gradient reverses the ATP-driven proton pump [9,13]. We have recently shown that it is possible to stimulate ATP synthesis both in acid-base transition and postillumination experiments by imposing a diffusion potential on a

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Section: Stimulation Of Postillumination a T P Synthesis By A Diffusupporting

confidence: 75%

Stimulation of ATP Synthesis by a Membrane Potential in Chloroplasts

Schuldiner

Rottenberg

Avron

1973

European Journal of Biochemistry

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“…The adjustment of the value of K c to K m requires the density values of the solutions. Thus, with the densities reported by Benzinger et al, (3) we obtain the value K m = 378 for reaction (5).…”

Section: Resultsmentioning

confidence: 78%

“…The values of r H o m determined in this study for reactions (5) and (6) (22) a Benzinger and Hems (2) did not report the pH at which their measurements were performed. We have assumed that the pH was the same as that used by Benzinger et al, (3) namely pH = 5.5. b It does not appear that a buffer was used in the equilibrium studies of Benzinger and Hems (2) or of Benzinger et al (3) in the literature are those of Benzinger et al (2,3) from which we obtain K c = 387 for reaction (5) at T = 298.15 K and I = 0. The adjustment of the value of K c to K m requires the density values of the solutions.…”

Section: Resultsmentioning

confidence: 99%

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A thermodynamic study of the hydrolysis of L-glutamine to (L-glutamate + ammonia) and of L-asparagine to (L -aspartate + ammonia)

Kishore

Tewari

Goldberg

2000

The Journal of Chemical Thermodynamics

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“…On the assumption that intracellular ATP concentration is 1-5 x 10-3 M, ADP concentration 0-32 x 103 M and Pi concentration 0'36 x 103 M (Bartlett et al 1953) and that the standard free energy change of ATP hydrolysis under physiological conditions is 7-2 kcal (Benzinger et al 1959 …”

Section: Discussionmentioning

confidence: 99%

Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells

Schatzmann¹

1973

The Journal of Physiology

336

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SUMMARY1. In resealed human red cells loaded with Ca-EGTA buffer solutions it was found that the intracellular free Ca2+ concentration for half saturation of the Ca transport system (which pumps Ca out of the cell) is equal to or smaller than 4 x 10-6 M and thus closely agrees with the dissociation constant of the Ca+ Mg activated membrane ATPase.2. The maximal rate of Ca transport from resealed cells to medium was found to be 0 148 + 0 009 #zmole/ml. cells.min at 280 C.3. The rate of Ca transport was unaffected by a variation of the extracellular Ca2+ concentration from 3-10-7 to 5-10-M.4. Evidence is presented making it probable that the stoichiometric relation between Ca transported and ATP hydrolysed is 1:1 rather than 2:1.5. As the Ca transport is quite rapid even at half saturation and the passive leak for Ca negligible in intact cells it can be predicted that the steady-state cellular Ca2+ concentration must be low, most probably less than 106 /imole/ml. cells. Transport from cells containing 5-10-7

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Free-energy changes of the glutaminase reaction and the hydrolysis of the terminal pyrophosphate bond of adenosine triphosphate

Cited by 104 publications

References 19 publications

Stimulation of ATP Synthesis by a Membrane Potential in Chloroplasts

Stimulation of ATP Synthesis by a Membrane Potential in Chloroplasts

A thermodynamic study of the hydrolysis of L-glutamine to (L-glutamate + ammonia) and of L-asparagine to (L -aspartate + ammonia)

Dependence on calcium concentration and stoichiometry of the calcium pump in human red cells

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