Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Anoxia has been compared with ischaemia. The abrupt restoration of either oxygen of flow may accelerate cardiac damage. Anoxic stimulation of glycolysis (Pasteur effect) is inhibited during ischaemia by lactate and proton accumulation at the levels of phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase. Anaerobic glycolysis provides lactate and ATP; breakdown of the latter provides protons. During partial respiration thought to occur in partial ischaemia, continued production of CO2 is a factor contributing to intracellular acidosis; mitochondrial ATP when formed by continued respiration also yields protons when ultimately broken down. The endoproducts of aerobic glycolysis (pyruvate and NADH) are transported into the mitochondria by the malate-aspartate cycle and by pyruvate dehydrogenase activity. Adenine nucleotide transferase activity normally transfers the mitochondrially-made ATP to the cytoplasm, but acyl CoA accumulates in ischaemia (or during perfusions with high circulating free fatty acids) to inhibit the transferase. The mitochondrial creatine kinase is thought to transform ATP transported outwards into creatine phosphate which can permeate the outer mitochondrial membrane. Further compartmentation of ATP may be by other creatine kinase isoenzymes or in relation to the cell membrane. The glycogenolytic-sarcoplasmic reticulum complex links a glycogen pool to the sarcoplasmic reticulum. Cyclic AMP may regulate admission of calcium to the cell during the plateau of the action potential and promote calcium uptake by the sarcoplasmic reticulum by phosphorylation of phospholamban. The latter promotes the activity of the calcium-transport ATPase. Calcium and cyclic AMP may also interact at the level of the contractile proteins where cyclic AMP phosphrylates troponin. Cyclic GMP generally has opposite effects to cyclic AMP and undergoes opposite changes in the frog cardiac cycle to those of cyclic AMP. A present it is reasonable to suppose that physiological effects of adrenaline or of cholinergic agents on the myocardium are mediated by cyclic AMP or cyclic GMP, respectively, but this hypothesis still lacks firm support. There is an association between tissue cyclic AMP and ventricular fibrillation after coronary ligation, and direct evidence for a role of cyclic AMP in promoting arrhythmias has been obtained by studies on the ventricular fibrillation threshold in the rat heart. However, there are other mechanisms, involving first the effects of substrates on the action potential duration, and secondly, the fast channel, which can also give rise to the development of malignant arrhythmias.
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PMID:Myocardial metabolism and heart disease. 3 41

Acute starvation of adult rats resulted in a rise in the electroconvulsive threshold at 48 hours (P less than .10) and at 72 hours (P less than .01), but not at 24 hours. Biochemical correlates included (1) ketonemia and mild hypoglycemia in the blood; (2) a significant rise in the brain cytoplasmic phosphorylation potential and in the energy charge potential; (3) a shift in the brain cytoplasmic oxidation-reduction potential to a more oxidized state; (4) probable partial inhibitions in brain phosphofructokinase and pyruvate dehydrogenase; and (5) relatively small increases in brain sodium (4.1%), potassium (2.4%), and chloride (4.3%). No major differences were seen in brain water content or adenosine triphosphatase activity. The observed cerebral biochemical alterations are believed to be the consequence of increased ketone body utilization, although the precise relationship to the alteration in the electroconvulsive threshold remains unclear.
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PMID:Starvation and seizures. Observation on the electroconvulsive threshold and cerebral metabolism of the starved adult rat. 12 78

The content of coenzyme A-SH (CoASH) and acetyl-CoA of suspensions of rat heart mitochondria was stabilized by the addition of DL-carnitine and acetyl-DL-carnitine, in the presence of the respiratory inhibitor rotenone. The mitochondrial content of NAD+ and NADH was similarly stabilized by the addition of acetoacetate and DL-3-hydroxybutyrate, and the content of ADP and ATP was imposed by the addition of these nucleotides to the mitochondrial suspension, in the presence of uncoupling agent and oligomycin, to inhibit ATPase. Under these conditions, mitochondrial CoASH/acetyl-CoA, NAD+/ NADH, and ADP/ATP ratios could be varied independently, and the effect on the interconversion of active and inactive pyruvate dehydrogenase could be studied. Decreases in both CoASH/acetyl-CoA and NAD+/NADH ratios were shown to be inhibitory to the steady state activity of pyruvate dehydrogenase, and this effect is described at three different ADP/ATP ratios and different concentrations of added MgCl2. A new steady state level of activity was achieved within 10 min of a change in either CoASH/acetyl-CoA or NAD+/NADH ratio; the rate of inactivation was much higher than the rate of reactivation under these conditions. Effects of CoASH/acetyl-CoA and NAD+/NADH may be additive but are still quantitatively lesser than the changes in activity of pyruvate dehydrogenase induced by changes in ADP/ATP ratio. The variation in activity of pyruvate dehydrogenase with ADP/ATP ratio is described in the absence of changes in the other two ratios, conditions which were not met in earlier studies which employed the oxidation of different substrates to generate changes in all three ratios.
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PMID:Studies on the effects of coenzyme A-SH: acetyl coenzyme A, nicotinamide adenine dinucleotide: reduced nicotinamide adenine dinucleotide, and adenosine diphosphate: adenosine triphosphate ratios on the interconversion of active and inactive pyruvate dehydrogenase in isolated rat heart mitochondria. 18 82

The mitochondrial matrix subfractions from rat liver, kidney cortex, brain, heart, and skeletal muscle were isolated and their protein components were resolved by two-dimensional polyacrylamide gel electrophoresis, revealing between 120 and 150 components for each matrix subfraction. Excellent resolution was obtained utilizing a pH 5 to 8 gradient in the first dimension and in 8 to 13% exponential acrylamide gradient in the second dimension, increasing the number of mitochondrial matrix proteins observed 3-fold over one-dimensional systems. Protein components tentatively identified by co-migration with pure enzymes and by known tissue distributions are carbamoyl-phosphate synthetase (EC 2.7.2.5), ornithine transcarbamylase (EC 2.1.3.3), glutamate dehydrogenase (EC 1.4.1.3), pyruvate carboxylase (EC 6.4.1.1), citrate synthase (EC 4.1.3.7), fumarase (EC 4.2.1.2), aconitase (EC 4.2.1.3), alpha-ketoglutarate dehydrogenase (EC 1.2.4.2), dihydrolipoyl transsuccinylase (EC 2.3.1.12), lipoamide dehydrogenase (EC 1.6.4.3), glutamate-aspartate aminotransferase (EC 2.6.1.1), and the two subunits of pyruvate dehydrogenase (EC 1.2.4.1). Protein components unambiguously identified by peptide mapping are citrate synthase, aconitase, and pyruvate carboxylase. The inner membrane subfraction from rat liver mitochondria was also resolved two dimensionally; the alpha and beta subunits of ATPase (F1) (EC 3.6.1.3) were identified by peptide mapping.
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PMID:Resolution of rat mitochondrial matrix proteins by two-dimensional polyacrylamide gel electrophoresis. 44 63

The relationships between Na/K pump activity and adenosine triphosphate (ATP) production were determined in isolated rat brain synaptosomes. The activity of the enzyme was modulated by altering [K+]e, [Na+]i, and [ATP]i while synaptosomal oxygen uptake and lactate production were measured simultaneously. KCl increased respiration and glycolysis with an apparent Km of about 1 mM which suggests that, at the [K+]e normally present in brain, 3.3-4 mM, the pump is near saturation with this cation. Depolarization with 6-40 mM KCl had negligible effect on ouabain-sensitive O2 uptake indicating that at the voltages involved the activity of the Na/K ATPase is largely independent of membrane potential. Increases in [Na+]i by addition of veratridine markedly enhanced glycoside-inhibitable respiration and lactate production. Calculations of the rates of ATP synthesis necessary to support the operation of the pump showed that greater than 90% of the energy was derived from oxidative phosphorylation. Consistent with this: (a) the ouabain-sensitive Rb/O2 ratio was close to 12 (i.e., Rb/ATP ratio of 2); (b) inhibition of mitochondrial ATP synthesis by Amytal resulted in a decrease in the glycoside-dependent rate of 86Rb uptake. Analyses of the mechanisms responsible for activation of the energy-producing pathways during enhanced Na and K movements indicate that glycolysis is predominantly stimulated by increase in activity of phosphofructokinase mediated via a rise in the concentrations of adenosine monophosphate [AMP] and inorganic phosphate [Pi] and a fall in the concentration of phosphocreatine [PCr]; the main moving force for the elevation in mitochondrial ATP generation is the decline in [ATP]/[ADP] [Pi] (or equivalent) and consequent readjustments in the ratio of the intramitochondrial pyridine nucleotides [( NAD]m/[NADH]m). Direct stimulation of pyruvate dehydrogenase by calcium appears to be of secondary importance. It is concluded that synaptosomal Na/K pump is fueled primarily by oxidative phosphorylation and that a fall in [ATP]/[ADP][Pi] is the chief factor responsible for increased energy production.
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PMID:Relationships between the neuronal sodium/potassium pump and energy metabolism. Effects of K+, Na+, and adenosine triphosphate in isolated brain synaptosomes. 215 72

We studied the metabolism of the conduction system and the working myocardium in diabetic rat hearts by enzyme histochemistry. The experiment was performed three weeks following the administration of streptozotocin (65 mg/kg) to male Wistar rats. The hearts were quickly excised and tissue was frozen immediately by immersion in isopentane at -30 degrees C and cut into 16 microns thick sections in a cryostat. The PAS positive reaction was increased in the conduction system compared to the working myocardium in control rats. In diabetic rat hearts, these reactions in the working myocardium and the conduction system were strongly increased compared to control hearts. Several enzyme activities, such as phosphofructokinase, pyruvate dehydrogenase, glucose-6-phosphate dehydrogenase, Na-K ATPase, were reduced in both the working myocardium and conduction system of diabetic rat hearts. These results suggest that the changes in metabolic condition also exist in the conduction system of the diabetic rat hearts as well as the working myocardium.
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PMID:Histochemical studies on the conduction system of diabetic rat hearts. 216 29

The steady-state content of active (dephospho) pyruvate dehydrogenase (PDHA) of suspensions of coupled rat brain mitochondria oxidizing succinate was found to be markedly increased with increasing free Ca2+ ion concentration of the medium, with a half-maximal effect at 10(-6.43) M Ca2+. Other ions were present in these studies at concentrations appropriate for the cytosol. Depolarization of the plasma membrane of synaptosomes caused an increase in the steady-state content of PDHA, with veratridine giving a larger increase than depolarization by 33 mM-KCl. Values were 68 +/- 1% (n = 13) and 81 +/- 1% (n = 19) of maximal activity, for control incubations and incubations in the presence of 30 microM-veratridine, respectively. Measurements of cytosolic free Ca2+ concentrations ([Ca2+]cyt.) in these suspensions of synaptosomes, with the use of the fluorescent Ca2+-indicator Quin-2, indicated an increase on depolarization, with the change due to 30 microM-veratridine being larger in extent than that due to 33 mM-KCl. Values were 217 +/- 21 nM (n = 15), 544 +/- 48 nM (n = 15) and 783 +/- 75 nM (n = 14) for control, KCl-depolarized and veratridine-depolarized synaptosomes respectively. Experiments in which synaptosomes were treated with Ruthenium Red, an inhibitor of mitochondrial Ca2+ uptake, gave much lower resting contents of PDHA (42 +/- 2% of maximal), but failed to prevent totally an increase on depolarization. Addition of an excess of EGTA to the synaptosomal suspension just before the addition of veratridine resulted in a partial diminution in the response of PDHA content. Parallel studies with Quin-2 indicated no increase in [Ca2+]cyt. on addition of veratridine, under these conditions. Thus an increase in [Ca2+]cyt. forms only a part of the mechanism whereby pyruvate dehydrogenase interconversion responds to depolarization. A decrease in the ATP/ADP ratio may also be important, as inferred from the results of experiments with ouabain, which inhibits the Na+ + K+-dependent ATPase.
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PMID:Role of Ca2+ in pyruvate dehydrogenase interconversion in brain mitochondria and synaptosomes. 258 58

Autoantibodies present in the disease primary biliary cirrhosis react by immunoblotting with four major yeast mitochondrial antigens of 58 kDa, 55 kDa, 52 kDa and 45 kDa, tentatively identified as the lipoate acetyl transferases (E2) of the pyruvate dehydrogenase, component X of E2 pyruvate dehydrogenase, E2 of 2-oxo glutarate dehydrogenase and E2 of branched-chain 2-oxo acid dehydrogenase complexes respectively. The synthesis of these antigens is sensitive to catabolite repression. The reactive antigens are present in mit- mutants of yeast which have specific defects in the mitochondrial apocytochrome b, cytochrome oxidase subunit II and H+ -ATPase subunits 8 and 9, and in mtDNA-less rho O petite mutants, but a significant increase in the sensitivity to catabolite repression was observed in these mutants in particular in the mtDNA-less strains.
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PMID:Anti-mitochondrial autoantibodies of primary biliary cirrhosis as a novel probe in the study of the biosynthetic regulation of the yeast 2-oxo acid dehydrogenase complexes. 264 31

The process of interaction of gossypol with sperm macromolecules is critical to an understanding of gossypol's mechanism of action. Experimental results suggest that gossypol influences enzyme systems of sperm involved in the production and utilization of ATP and that the drug interacts with macromolecules by Schiff base formation and hydrophobic interaction. Gossypol acts on the mitochondria, suppressing oxygen consumption, inhibiting pyruvate dehydrogenase and ATPase activities, and probably on the sperm motility apparatus by blocking dynein ATPase activity and preventing protein phosphorylation.
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PMID:Interaction of gossypol with sperm macromolecules and enzymes. 296 57

Mitochondria from bovine hearts were fractionated by three different procedures and the fractions were characterized by marker enzymes. Highly purified outer membranes, membrane vesicles, and inner membranes, as well as two high-speed soluble fractions, were obtained. Azide (or oligomycin) resistant ATPase was not found to be a marker for outer membranes. The data were consistent with the association of the protein kinase activity with the soluble matrix of the mitochondria. Activity was highest with histone H2B as the substrate, with histone H1 next in preference. In contrast to the mitochondrial protein kinases studied previously, protamine, casein, and phosvitin were very poor substrates and there was no detectable phosphorylation of pyruvate dehydrogenase. Activity was stimulated by cAMP but not by cGMP, calmodulin, or phosphatidylserine--diolein, with or without Ca2+. Two cAMP-dependent isozymes were separated from the soluble fraction of the mitochondria by chromatography on DE-52 columns. Phosphorylation of histone H2B by the isozymes was inhibited by 98% by Kemptide.
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PMID:cAMP-dependent protein kinase isozymes with preference for histone H2B as substrate in mitochondria of bovine heart. 382 13


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