The Enthalpy Change of the Hydrolysis of Adenosine Triphosphate by Rat Liver Mitochondria

1971 ◽  
Vol 49 (6) ◽  
pp. 721-729 ◽  
Author(s):  
Roberto Cereijo-Santaló
Keyword(s):  
Rat Liver ◽  
Atp Hydrolysis ◽  
Liver Mitochondria ◽  
Enthalpy Change ◽  
Rat Liver Mitochondria ◽  
Kcal Mole ◽  
Time Limits ◽  
Differential Calorimeter ◽  
Hydrolysis Of ◽  
Enthalpy Of Ionization

The enthalpy change of the hydrolysis of ATP by rat liver mitochondria was studied using a differential calorimeter. This calorimeter is capable of working as a perfect adiabatic system within the time limits and temperature gradients of our experiments. Samples can be withdrawn from the incubation medium without interference with the temperature measurements.The enthalpy of ionization of Tris was found to be −11.28 ± 0.17 kcal mole−1. The enthalpy of ATP hydrolysis in the presence of either 2,4-dinitrophenol or valinomycin was −6.2 ± 0.1 kcal mole−1.

scholarly journals Characterization of phosphate efflux pathways in rat liver mitochondria

1983 ◽  
Vol 212 (2) ◽  
pp. 279-288 ◽  
Author(s):  
R S Kaplan ◽  
P L Pedersen
Keyword(s):  
Rat Liver ◽  
Transport System ◽  
Atp Hydrolysis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Current View ◽  
Mitochondrial Inner Membrane ◽  
Efflux Pathway ◽  
Hydrolysis Of

ATP hydrolysis catalysed by the H+-ATPase of intact mitochondria can be induced by addition of ATP in the presence of valinomycin and KCl. This leads to an increase in intramitochondrial Pi and therefore allows investigation of potential Pi efflux pathways in intact mitochondria. Combining this approach with the direct measurement of both internal and external Pi, we have attempted to determine whether Pi efflux occurs via an atractyloside-sensitive transporter, by the classical operation of the Pi/H+ and Pi/dicarboxylate carriers, and/or by other mechanisms. Initial experiments re-examined the evidence that led to the current view that one efflux pathway for Pi is an atractyloside-sensitive ATP/ADP,0.5Pi transporter. No evidence was found in support of this efflux pathway. Rather, atractyloside-sensitivity of the low rate of Pi efflux observed in previous studies (oligomycin present) was accounted for by ATP entry on the well known ATP/ADP transport system followed by hydrolysis of ATP and subsequent Pi efflux. Thus, under these conditions, where ATP hydrolysis is not completely inhibited, Pi efflux becomes atractyloside sensitive most likely because this inhibitor blocks ATP entry, not because it directly inhibits Pi efflux. Substantial efflux of Pi from rat liver mitochondria is observed on generation of high levels of matrix Pi by ATP hydrolysis induced by valinomycin and K+ (oligomycin absent). A portion of this efflux can be inhibited by thiol-specific reagents at concentrations that normally inhibit the Pi/H+ and Pi/dicarboxylate carriers. However, a significant fraction of efflux continues even in the presence of p-chloromercuribenzoate, N-ethylmaleimide plus n-butylmalonate or mersalyl. The mersalyl-insensitive Pi efflux, which is also insensitive to carboxyatractyloside, is a saturable process, thus suggesting carrier mediation. During this efflux the mitochondrial inner membrane retains considerable impermeability to other low-molecular-weight anions (i.e., malate, 2-oxoglutarate). In conclusion, results presented here rule out an atractyloside-sensitive ATP/ADP,0.5Pi transport system as a mechanism for Pi efflux in rat liver mitochondria. Rather Pi efflux appears to occur on the classical Pi/H+ transport system as well as via a mersalyl-insensitive saturable process. The inhibitor-insensitive Pi efflux may occur on a portion of the Pi/H+ carrier molecules that exist in a state different from that normally catalysing Pi influx. Alternatively, a separate Pi efflux carrier may exist.

scholarly journals The synthesis of hippurate from benzoate and glycine by rat liver mitochondria. Submitochondrial localization and kinetics

1977 ◽  
Vol 166 (1) ◽  
pp. 39-47 ◽  
Author(s):  
S J Gatley ◽  
H S A Sherratt
Keyword(s):  
Rat Liver ◽  
Atp Hydrolysis ◽  
Atp Synthesis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
O2 Consumption ◽  
Mitochondrial Content ◽  
Presence And Absence ◽  
The Individual ◽  
Good Agreement

1. Rat liver mitochondria make hippurate at up to 4 nmol/min per mg of protein. The rate of synthesis supported by oxidation of glutamate with exogenous Pi present is identical with that supported by ATP plus oligomycin. Lower rates were obtained with other respiratory substrates, and when glutamate was used without Pi. 2. A matrix localization for hippurate synthesis is indicated by the latency of benzoyl-CoA synthetase and glycine N-acyltransferase to their extramitochondrial substrates, failure of exogenous benzoyl-CoA to inhibit incorporation of [14C]hippurate and inhibition of hippurate synthesis supported by ATP, but not glutamate, by carboxyatractyloside. 3. The relative activities of the individual enzymes and the mitochondrial content of benzoyl-CoA in the presence and absence of glycine suggest that hippurate synthesis is rate-limited by formation of benzoyl-CoA. 4. The increases in rates of ATP hydrolysis and of O2 consumption on the addition of benzoate and glycine were in good agreement with those required to support hippurate synthesis. The increase in respiration indicates that State-4 respiration [Chance & Williams (1957) Adv. Enzymol 17, 65-134] is not used, with these conditions, for ATP synthesis.

scholarly journals ATP Prevents both Hydroperoxide-Induced Hydrolysis of Pyridine Nucleotides and Release of Calcium in Rat Liver Mitochondria

1981 ◽  
Vol 117 (2) ◽  
pp. 361-367 ◽  
Author(s):  
Tony MÜHLEBACH ◽  
Hans-Ruedi LÖTSCHER ◽  
Kaspar H. WINTERHALTER ◽  
Christoph RICHTER ◽  
Willy HOFSTETTER
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Pyridine Nucleotides ◽  
Hydrolysis Of

scholarly journals Effects of calmodulin antagonists on the active Ca2+ uptake by rat liver mitochondria

1983 ◽  
Vol 214 (3) ◽  
pp. 929-935 ◽  
Author(s):  
M G P Vale ◽  
A J M Moreno ◽  
A P Carvalho
Keyword(s):  
Rat Liver ◽  
Atp Hydrolysis ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Atpase ◽  
Calmodulin Antagonists ◽  
Carrier System ◽  
Specific Substance ◽  
Phenothiazine Drugs ◽  
Mitochondrial Atpase Activity

The mechanism of Ca2+ transport by rat liver mitochondria was investigated with respect to the possible involvement of calmodulin in this process. We studied the action of exogenous calmodulin isolated from brain tissue on the Ca2+-transport system, as well as the effect of two types of calmodulin antagonists; the phenothiazine drugs trifluoperazine and chlorpromazine and the more specific substance compound 48/80. Our results show that Ca2+ transport by mitochondria and mitochondrial ATPase activity are insensitive to exogenous calmodulin, although they can be inhibited by the phenothiazines. Since no effect of compound 48/80 was observed, we believe that the phenothiazines act through a mechanism that does not involve calmodulin. This is in accord with our inability to locate significant quantities of calmodulin in mitochondria by radioimmunoassay analysis. Our results further show that trifluoperazine and chlorpromazine also inhibit the electron-carrier system of the respiratory chain, and this effect may mediate their inhibitory action on Ca2+ transport when it is energized by respiration instead of ATP hydrolysis.

Biosynthesis of Mitochondrial Phospholipids Using Endogenously Generated Diglycerides

1975 ◽  
Vol 53 (7) ◽  
pp. 784-795 ◽  
Author(s):  
W. C. McMurray
Keyword(s):  
Endoplasmic Reticulum ◽  
Phosphatidic Acid ◽  
Phospholipase C ◽  
Rat Liver ◽  
De Novo ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Isolated Mitochondria ◽  
Hydrolysis Of ◽  
Stimulation Of

When isolated mitochondria or microsomes from rat liver were treated with phospholipase C, the incorporation of radioactive phospholipid precursors was markedly enhanced, presumably as a result of production of diglycerides by hydrolysis of endogenous phospholipids. Incorporation of CDP[14C]choline into lecithin in rat liver or BHK-21 mitochondria could be attributed to residual contamination from elements of the endoplasmic reticulum, with added diglycerides or with endogenous diglycerides produced by the phospholipase C treatment. A similar stimulation of [γ32P]ATP incorporation into phospholipids was observed with exogenous or endogenous diglycerides, but the mitochondrial diglyceride kinase in either case was also related to the degree of microsomal contaminants. It was concluded that previous studies showing negligible capacity of mitochondria for lecithin biosynthesis de novo were not explainable on the basis of limited accessibility of added diglycerides, and that formation of phosphatidic acid by diglyceride kinase was not of significance in rat liver mitochondria.

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