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)

Free-flow electrophoresis was used to subfractionate membrane vesicles from calf thymocyte plasma membranes. The fractionation resulted in a separation of vesicle populations bearing four different enzymes: alkaline nitrophenyl-phosphatase (orthophosphoric-monoester phosphohydrolase (alkalin optimum) EC 3.1.3.1), gamma-glutamyltransferase (EC 2.3.2.2), (Mg2+ + Na+ + K+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) and acyl-CoA:lysophosphatidylcholine acyltransferase (acyl-CoA:1-acylglycero-3-phosphocholine-O-acyltransferase, EC 2.3.1.23). The specific content of cholesterol and total phospholipid coincided with the distribution of membrane-bound protein. However, vesicles migrating towards the cathode had a higher molar ratio of cholesterol to phospholipid (0.75) compared to those migrating to the anode (0.55). Sodium dodecyl sulphate-gel electrophoresis of pooled vesicle fractions also demonstrates distinct differences in their protein pattern. Electron-micrographic thin sections show that the vesicle populations have a similar morphology and size distribution. These results are discussed in terms of heterogeneity of the original thymocytes, contamination with intracellular membranes and a heterogeneous structure of the plasma membrane.
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PMID:Fractionation of membrane vesicles. II. A method for separation of membrane vesicles bearing different enzymes by free-flow electrophoresis. 2 91

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

ATP synthase preparations [complex V, proton-translocatin ATPase (adenosine triphosphatase) and oligomycin-sensitive ATPase ] contain stoicheiometric amounts of lipoic acid residues (up to 6mol of lipoic acid/mol of ATPase complex) and catalyse net ATP synthesis in an uncoupler-and oligomycin-sensitive reaction utilizing dihydrolipoate, oleoyl-CoA and oleic acid, or in a reaction utilizing oleoyl-S-lipoate. The terminal reactions of oxidative phosphorylation are thus analogous to those of substrate-level phosphorylation.
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PMID:Studies of energy-linked reactions. Net synthesis of adenosine triphosphate by isolated adenosine triphosphate synthase preparations: a role for lipoic acid and unsaturated fatty acids. 13 19

Muscle biopsy samples were obtained from healthy subjects in order to evaluate quantitative differences in single fibres of substrate (glycogen and triglyceride) and ion concentrations (Na+ and K+) as well as enzyme activity levels (succinate-dehydrogenase, SDH; phosphofructokinase, PFK; 3-hydroxyacyl-CoA-dehydrogenase, HAD; myosin ATPase) between human skeletal muscle fibre types. After freeze drying of the muscle specimen fragments of single fibres were dissected out and stained for myofibrillar-ATPase with preincubations at pH's of 10.3, 4.6, 4.35. Type I ("red") and II A,B, and C ("white") fibres could then be identified. Glycogen content was the same in different fibres, whereas triglyceride content was highest in Type I fibres (2-3 X Type II). No significant differences were observed for Na+ and K+ between fibre types. The activity for the enzymes studied were quite different in the fibre types (SDH and HAD, Type I is approximately 1.5 X Type II; PFK Type I is approximately 0.5 X Type II, Myosin ATPase Type I is approxiamtely 0.4 X Type II). The subgroups of Type II fibres were distinguished by differences in both SDH and PFK activities (SDH, Type II C is greater than A is greater than B; PFK, Type II B is greater than A is approximately C). It is concluded that contractile and metabolic characteristics of human skeletal fibres are very similar to many other species. One difference, however, appears to be than no Type II fibres have an oxidative potential higher than Type I fibres.
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PMID:Metabolic characteristics of fibre types in human skeletal muscle. 24 87

1. Conditions for the optimal coupled oxidation by rat liver mitochondria of long-chain free fatty acids were defined. The fatty acids studied were in the omega9 series: oleic (18 : 1), gondoic (20 : 1) and erucic (22 : 1) acids. Carnitine (about 0.1 mM) maximally stimulated State 3 respiration due to oleic and gondoic acids about three-fold (coenzyme A present), and coenzyme A (10--20 micrometer) stimulated about two-fold (carnitine present). When neither coenzyme A nor carnitine was added, respiration was very slow. 2. When respiration was limited by ADP, concentrations of added CoA only slightly in excess of that required for fatty acid oxidation very significantly decreased the ATP/ADP ratio maintained at a given rate of respiration imposed by externally added ATPase, and increased the level of membrane-associated acyl-CoA. This effect was most pronounced with oleic acid, and least with erucic acid. When excess ADP was present, higher concentrations of added coenzyme A (50--200 micrometer) inhibited to oxidation of oleic acid in a concentration-dependent manner, whereas the oxidation of substrates other than fatty acids was essentially unaffected. 3. It is concluded that, in addition to its requirement for fatty acid oxidation, coenzyme A exerts two independent effects on mitochondrial metabolism as here determined in vitro: (a) under conditions mimicking those in the intact cell with respect to phosphorylation-dependent respiration (ADP limiting), acyl-CoA formed from added coenzyme A and fatty acid inhibits the adenine nucleotide translocase, resulting in a lowering in the extramitochondrial ATP/ADP ratio obtained at any given rate of phosphorylation-limited respiration, and (b) under State 3 conditions (ADP in excess) coenzyme A ( less than 50--200 micrometer) specifically suppresses oxidation of long-chain fatty acids by limiting the rate of formation of intramitochondrial acyl-CoA.
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PMID:The effects of coenzyme A and carnitine on steady-state ATP/ADP ratios and the rate of long-chain free fatty acid oxidation in liver mitochondria. 63 40

The postnatal development of mitochondrial ATP-producing pathways and Na-K-adenosinetriphosphatase (ATPase) in the rat medullary thick ascending limb of Henle (MTAL) was studied by measuring the activities of 3-ketoacid-CoA transferase, fumarase, citrate synthase, and Na-K-ATPase in microdissected MTAL of 16, 21, and 30-day-old pups and in adults. The role of adrenal steroids in the development of these four markers was also investigated by studying 21-day-old rats adrenalectomized on day 16 and given dexamethasone or aldosterone or NaCl injections from day 16 to day 21. There were large and correlated increases in the activities of the oxidative enzymes in the MTAL of control rat kidneys between 16 and 30 days after birth; Na-K-ATPase activity in the MTAL also greatly increased during the same period. Adrenalectomy completely prevented the developmental increases in MTAL oxidative enzymes and Na-K-ATPase; dexamethasone restored the development of all four enzymes, whereas aldosterone had no effect. We conclude that the postnatal maturation of Na+ reabsorption functions in MTAL cells involves coordinated increases in the capacity to produce ATP by oxidative metabolism and in Na-K-ATPase activity. This maturation process is probably triggered by the rise in circulating glucocorticoids that occurs during the weaning period.
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PMID:Coordinate development of oxidative enzymes and Na-K-ATPase in thick ascending limb: role of corticosteroids. 132 5

Selected enzymes of energy metabolism were measured in random individual fibers of soleus and tibialis anterior (TA) muscles from rats exposed for 2 wk to spaceflight (F) aboard COSMOS 2044 or tail suspension (T) and from synchronous controls. Average size of soleus fibers (dry weight per unit length) was reduced 37% in F and T fibers; there was little change in TA fibers. Enzyme changes were more pronounced in soleus than in TA fibers. Three enzymes characteristic of fast-twitch muscles, pyruvate kinase, glycerol-3-phosphate dehydrogenase, and 1-phosphofructokinase, were elevated in F and T soleus fibers, but changes in phosphofructokinase were not statistically significant. 3-Ketoacid-CoA transferase, characteristic of slow-twitch muscles, did not change significantly in either F or T fibers. Hexokinase, usually moderately higher in slow- than in fast-twitch muscles, increased markedly in both F and T fibers. In TA fibers analyzed for hexokinase, malate dehydrogenase, phosphohexoisomerase, and pyruvate kinase, only hexokinase and malate dehydrogenase showed significant changes. Hexokinase increased 83% in one of two T muscles. Enzyme data for TA fibers typed by myosin adenosinetriphosphatase were more informative: phosphofructokinase, phosphorylase, and glycerol-3-phosphate dehydrogenase were increased in type IIb fibers of either F or T muscles or both. Malate dehydrogenase was not changed in fibers of any type in either F or T muscle.
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PMID:Effects of microgravity and tail suspension on enzymes of individual soleus and tibialis anterior fibers. 138 50

Cytosolic free Ca2+ rises in pancreatic beta-cells in response to glucose stimulation and is part of the coupling to insulin secretion. This study evaluates a possible role for cytosolic long chain acyl-CoA esters in modulating Ca2+ handling by clonal beta-cells (HIT). Intact cells incubated with 20 microM free palmitic acid exhibited a 40% decrease in basal cytosolic free Ca2+. In contrast, acyl-CoA esters, up to a chain length of 16, but not the corresponding fatty acids, significantly lowered the Ca2+ set point maintained by cells permeabilized with saponin. The maximum response to the various acyl-CoA esters increased with increasing chain length, with no differences in the half-maximally effective concentration of 0.5 microM. Long chain acyl-CoA esters caused a 40-50% increase in 45Ca2+ influx into a non-mitochondrial pool in the permeabilized HIT cells, consistent with a stimulatory effect on the endoplasmic reticulum Ca(2+)-ATPase activity, but did not affect inositol 1,4,5-trisphosphate-induced Ca(2+)-efflux. Thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase activity, blocked the decrease in the Ca2+ set point caused by acyl-CoA esters. The ability of acyl-CoA esters to lower the Ca2+ set point depended on the ATP/ADP ratio (or free ADP); the Ca2+ set point was lowered by 36 +/- 3.6% at an ATP/ADP ratio of 90 and by 14 +/- 1.9% at an ATP/ADP ratio of 7. Depletion of cellular protein kinase C did not prevent the acyl-CoA-induced lowering of the Ca2+ set point. These findings suggest that the increases in long chain acyl-CoA esters may play a role in restoring cytosolic free Ca2+ through activation of Ca(2+)-ATPases.
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PMID:Acyl-CoA esters modulate intracellular Ca2+ handling by permeabilized clonal pancreatic beta-cells. 140 Mar

Citrobacter diversus ATCC 27156 was able to grow by decarboxylation of malonate to acetate under strictly anaerobic conditions, in the presence of yeast extract. The growth yield, corrected for growth on yeast extract, was 2.03 g cell dry mass per mol malonate. The addition of malonate to ATP-depleted cell suspensions (less than 0.2 nmol ATP/mg cell protein) resulted in a rapid increase in cellular ATP levels to between 4.5 and 6.0 nmol/mg cell protein. Intact cells decarboxylated malonate at rates of up to 1.5 mumol/min.mg protein. Enzyme assays on malonate-grown cells indicated activation of malonate by an ATP-dependent ligase reaction and by CoA transfer from acetyl-CoA, followed by decarboxylation of malonyl-CoA to acetyl-CoA with subsequent recovery of the invested ATP by substrate level phosphorylation through the activity of acetate kinase. Net ATP synthesis is postulated to be mediated by gradient formation coupled to the decarboxylation of malonyl-CoA. The protonophore CCCP and H(+)-ATPase inhibitor DCCD significantly reduced cellular ATP levels, suggesting a role for proton gradients in the energy metabolism of this strain when growing an malonate. Inhibitors of sodium metabolism or ommission of sodium had no effect on ATP levels or malonate decarboxylation.
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PMID:Anaerobic malonate decarboxylation by Citrobacter diversus. Growth and metabolic studies, and evidence of ATP formation. 151 May 73

The purpose of this study was to investigate the energy movement of the normothermic ischemic liver. Liver ischemia was induced in normal and cirrhotic rats, by cross-clamping portal vein and hepatic artery, bypassing the portal blood to the jugular vein through a shunt tube. The levels of ATP of the hepatic tissue was measured before and after hepatic ischemia, by HPLC and 31P-NMR. Before hepatic ischemia, the levels of ATP was greater in normal liver than in cirrhotic liver, but after ischemia it was significantly smaller in normal liver than cirrhotic liver. Generally they say that the greater is the ATP of the tissue, the greater is the viability of the tissue. But this experiment showed the contrary. Cirrhotic liver can't use glucose sufficiently, therefore acetyl-CoA, which is used in TCA-cycle, is derived from the resolution of fatty acid. As a result, free fatty acid and acyl-CoA increase in cirrhotic liver, and suppress Na(+)-K(+)-ATPase. I conclude that the cirrhotic liver can't effectively use ATP to maintain the potential of the liver cells, maybe, because of it's abnormal metabolism of glucose. Therefore, the levels of ATP was greater in cirrhotic liver than in normal liver after hepatic ischemia.
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PMID:[Investigation of hepatic energy metabolism in normothermic hepatic ischemia--comparison between normal and cirrhotic rat liver]. 154 96


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