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)

Multiple infarcts were produced in cerebral hemispheres of rats by injecting calibrated 50-micron microspheres into the left internal carotid artery, and alterations in lipid and energy metabolism were evaluated 24 hours later in the embolized hemisphere. Total phospholipid content was decreased by 26%, but the different classes of phospholipids were not equally affected. Phosphatidylinositol and phosphatidylserine levels were decreased by about 40% and phosphatidylcholine and phosphatidylethanolamine by 25%, while sphingomyelin level remained unchanged. There was a 3.2-fold increase in total free fatty acid content with a relatively larger rise in polyunsaturated free fatty acids 20:4 and 22:6 (20-fold increase). Determination of enzyme activities showed decreases in Na+,K+-ATPase (-21%) and hexokinase (-14%) but no changes in phosphofructokinase and pyruvate kinase. Study of energy metabolism using the closed system method of Lowry et al showed a significant depression (-36%) of the cerebral metabolic rate. Taken together, these data suggest a relation between lipid alterations and dysfunction of energy metabolism. Phospholipid degradation with subsequent free fatty acid release and alteration in membrane-bound enzymes may have a direct effect on metabolic machinery and may slow cerebral metabolic rate.
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PMID:Lipid metabolism, cerebral metabolic rate, and some related enzyme activities after brain infarction in rats. 356 99

In the process of defining the recruitment of fuel and pathway selection in rainbow trout fast-twitch white skeletal muscle, it was clear that the near-maximal myosin adenosinetriphosphatase activity during a 10-s sprint was supported solely by phosphocreatine hydrolysis. A conservative estimate of the ATP turnover was 188 mumol X g wet wt-1 X min-1. It was not until the rate and force of contraction decreased that the relative contribution of anaerobic glycogenolysis became increasingly important. Over a 10-min period of burst swimming at approximately 120% of maximum aerobic steady-state swimming velocity of trout determined in a Brett-type swim tunnel, fatigue was associated with the near-depletion of glycogen in white muscle. The ATP turnover supported by anaerobic glycogenolysis was 78 mumol X g wet wt-1 X min-1. The glycolytic pathway appeared functional at this time with control sites being identified at hexokinase and phosphofructokinase (PFK-1). PFK-1 did not appear to be inhibited by low muscle pH (pH 6.66). In another exercise protocol lasting 30 min, complete exhaustion was related to glycogen depletion. The sum of all glycolytic intermediates from glucose 6-phosphate to pyruvate at exhaustion decreased by a dramatic 80% compared with the 25% decrease for the 10-min fatigue swimming protocol. This large depletion of glycolytic intermediates was accompanied by an 80% fall in ATP, a 70-80% reduction in the ATP/ADP and phosphorylation potential, and a 2.5-fold increase in the NAD/NADH. Associated with these changes was a marked displacement of the phosphoglycerate kinase (PGK), and the combined glyceraldehyde-3-phosphate dehydrogenase-PGK reactions from thermodynamic equilibrium. As a general conclusion, fatigue and exhaustion should be viewed as a multicomponent biochemical process in response to low glycogen and not leveled at one particular step of the glycolytic pathway.
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PMID:Regulation of anaerobic ATP-generating pathways in trout fast-twitch skeletal muscle. 360 83

The storage lesion which limits the shelf life of human blood in blood banking is associated with a metabolic loss of 2,3-diphosphoglycerate and ATP. This metabolic loss is driven by intracellular ATPase which are usually considered to include the ion pumps and the reactions which maintain the discoid shape of the human erythrocyte. Under the acidic conditions of blood storage, the energy-yielding reactions of the glycolytic pathway are restricted at the hexokinase and phosphofructokinase steps. We show here that under such circumstances the enzyme of the diphosphoglycerate shunt, diphosphoglycerate mutase/phosphatase and the glycolytic enzyme phosphoglycerate kinase can form a futile cycle with ATPase activity. This ATPase activity responds to 2-phosphoglycolate which is known to activate both diphosphoglycerate mutase and diphosphoglycerate phosphatase reactions. When the enzymes of the futile cycle are combined with the enzymes of the lower glycolytic pathway in a reconstitution experiment designed to represent conditions within the stored erythrocyte, the futile cycle does provide an ATPase activity which results in the metabolic loss of 2,3-diphosphoglycerate. An isotope incorporation experiment demonstrates that the futile cycle is active in glucose-depleted erythrocytes.
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PMID:A futile cycle in erythrocyte glycolysis. 406 53

1. Intracellular concentrations of intermediates and cofactors of glycolysis were measured in guinea-pig cerebral cortex slices incubated under varying conditions. 2. Comparison of mass-action ratios with apparent equilibrium constants for the reactions of glycolysis showed that hexokinase, phosphofructokinase and pyruvate kinase catalyse reactions generally far from equilibrium, whereas phosphoglucose isomerase, aldolase, phosphoglycerate kinase, phosphoglycerate mutase, enolase, adenlyate kinase and creatine phosphokinase are generally close to equilibrium. The possibility that glyceraldehyde 3-phosphate dehydrogenase may catalyse a ;non-equilibrium' reaction is discussed. 3. Correlation of changes in concentrations of substrates for enzymes catalysing ;non-equilibrium' reactions with changes in rates of glycolysis caused by alteration of the conditions of incubation showed that hexokinase, phosphofructokinase, pyruvate kinase and possibly glyceraldehyde 3-phosphate dehydrogenase are subject to metabolic control in cerebral cortex slices. 4. It is suggested that the glycolysis is controlled by two regulatory systems, the hexokinase-phosphofructokinase system and the glyceraldehyde 3-phosphate dehydrogenase-pyruvate kinase system. These are discussed. 5. It is concluded that the rate of glycolysis in guinea-pig cerebral cortex slices is limited either by the rate of glucose entry into the slices or by the hexokinase-phosphofructokinase system. 6. It is concluded that addition of 0.1mm-ouabain to guinea-pig cerebral cortex slices causes inhibition of either glyceraldehyde 3-phosphate dehydrogenase or phosphoglycerate kinase or both, in a manner independent of the known action of ouabain on the sodium- and potassium-activated adenosine triphosphatase.
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PMID:Control of glycolysis in cerebral cortex slices. 422 84

1. Methods of homogenizing suspensions of washed mammalian spermatozoa were studied. The most useful methods were those using sonication and those using a French press. 2. Hexokinase, phosphofructokinase, glucose phosphate isomerase and adenosine triphosphatase activities in ram, bull and boar spermatozoa were investigated by using these two homogenization methods. Glucose phosphate isomerase, representative of soluble cytoplasmic material, was very readily extracted and remained entirely in the supernatant after centrifugation at 145000g for 60min. In contrast, the other three activities were less easily extracted and were sedimented in various proportions under the described conditions of centrifugation. 3. Attempts to obtain subcellular fractions from sperm homogenates by ;classical' methods failed, owing apparently to the inhomogeneity of subcellular particles in the homogenates. It is concluded that, after removal of sperm heads, the only meaningful fractionation is a separation of spermatozoal material which sediments at 145000g during 60min from that which does not. 4. The stabilities of hexokinase and phosphofructokinase activities in bull, boar and ram sperm homogenates were investigated. Hexokinases showed very little dependence on the various environments tested, whereas the optimum conditions for phosphofructokinase stability were: a minimum of sonication, the presence of phosphate ions and of a thiol-group protectant, and a pH7.5. Activities of hexokinase, phosphofructokinase and glucose phosphate isomerase per sperm cell were compared with published data on rates of fructolysis by spermatozoa; the potential catalytic activities were shown to be considerably in excess of these rates. However, phosphofructokinase may be the rate-limiting enzyme of glycolysis in vivo in bull and ram spermatozoa.
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PMID:Glycolytic enzymes in mammalian spermatozoa. Activities and stabilities of hexokinase and phosphofructokinase in various fractions from sperm homogenates. 425 94

Exposure of red cells to fluoride produces a variety of metabolic alterations, most of which are based upon the secondary effects of enolase inhibition, which reduces pyruvate synthesis and interferes with the regeneration of diphosphopyridine nucleotide (NAD). Adenosine triphosphate (ATP) is consumed in the hexokinase and phosphofructokinase reactions but is not regenerated since the deficiency of NAD limits glyceraldehyde phosphate dehydrogenase. ATP depletion in the presence of fluoride and calcium induces a massive loss of cations and water. Of the other known sites of ATP utilization, membrane-bound ATPase is inhibited by fluoride, but the incorporation of fatty acids into membrane phospholipids is unaffected until ATP is depleted. The addition of methylene blue to fluoride-treated red cells regenerates NAD, permitting triose oxidation and the generation of 3-phosphoglycerate and 2,3-diphosphoglycerate. Enolase inhibition is then partially overcome by mass action, and sufficient glycolysis proceeds to maintain the concentration of ATP. This in turn prevents the massive cation and water loss, and permits membrane phospholipid renewal to proceed. Membrane ATPase activity is not restored by the oxidant so that normal cation leakage remains unopposed by cation pumping in red cells exposed to the combination of fluoride and methylene blue.
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PMID:Energy metabolism in human erythrocytes. I. Effects of sodium fluoride. 432 3

Mg2+-ATPase activity was identified in the cytosol of human erythrocytes. A partial purification of this activity was achieved by an initial DEAE-Sephadex column chromatography, followed by gel filtration on Sephadex G-100 and then a second DEAE-Sephadex chromatography procedure. The enzyme appeared in the void volume of the Sephadex G-100 column and was retained on an Amicon XM100A ultrafiltration membrane. The molecular weight of the enzyme was estimated to be 113 000 from SD gels. The above purification protocol yielded an enzyme with an optimal pH between 7.6 and 8.2. The enzyme activity increased linearly between 30 and 44 degrees C. It was stable for several months at -20 degrees C. Magnesium was essential for activity, but the rate attainable with Mn2+ was at least as great as that due to Mg2+. No other divalent cation was able to substitute for Mg2+ or Mn2+. Neither low nor high Ca2+ concentrations significantly affected the enzymatic activity. Substrate specificity studies showed that ATP was the preferred substrate followed by CTP (46% of the rate produced by ATP). Hydrolysis of GTP, UTP, ITP and ADP was less than 10% of the rate seen with ATP. No phosphatase, pyrophosphatase, phosphodiesterase, hexokinase, phosphofructokinase or adenylate cyclase activity could be detected in this enzyme preparation. Calmodulin, which stimulates the (Ca2+ + Mg2+)-ATPase of the human erythrocyte membrane, failed to enhance the Mg2+-ATPase activity. Of considerable interest, the activity of this Mg2+-ATPase was enhanced approximately 5-fold by low concentrations of mercuric ion, p-hydroxymercuribenzoate and DTNB, but was much less sensitive to iodoacetamide.
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PMID:Partial purification and characterization of a novel Mg2+-dependent ATPase present in the cytosol from human erythrocytes. 615 Jul 30

The activities of some enzymes of glycolysis, the citric acid cycle, and amino acid metabolism have been measured in the fetal guinea pig heart over the last third of gestation and correlated with heart ultrastructural development. There is little change in glycolytic enzyme activity except for a two- to threefold increase in phosphofructokinase activity. Mitochondrial content and enzyme activities are low in the early fetal heart, and, although content is similar in the late fetus and adult, enzyme activities increase twofold postnatally, indicating fetal heart mitochondria are incompletely developed. The activities of aspartate and particularly alanine aminotransferase are low in the fetal heart. Over the last third of gestation the myofibrillar content of the fetal myocyte increases twofold to the adult value by term. Associated with this is a fourfold rise in myofibrillar and sarcoplasmic reticulum Ca2+-ATPase activity. Na+-K+-ATPase activity is similar in the late fetal and adult heart but one-third lower in the early fetal heart.
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PMID:Ultrastructural and enzymatic development of fetal guinea pig heart. 621 93

A mathematical model was used to study the role of various allosteric regulatory mechanisms in the oxidation of glucose and fatty acids by muscle energy metabolism. A large number of such mechanisms were shown to be involved in simultaneous oxidation of both substrates: glycolysis is regulated by the ATP/ADP ratio at the phosphofructokinase (PFK) step; the control over pyruvate dehydrogenase is exercised by the NADHm/NADm+ and CoAsAc/CoAsH ratios as well as by the level of pyruvate; the Krebs cycle is regulated by oxaloacetate and citrate concentrations in the citrate synthase reaction and by the ATP/ADP and NADHm/NADm+ ratios in the isocitrate dehydrogenase reaction. The inhibition of PFK and pyruvate dehydrogenase by excess of CoAsAcyl as well as the inhibition of PFK by citrate are additional equivalent regulatory mechanisms. When glucose alone is oxidized, the levels of citrate, CoAsAcyl, NADHm and CoAsAc decrease drastically within the whole range of physiological ATPase loads; the only regulating factors that remain efficient are the ATP/ADP ratio in glycolysis, the level of pyruvate at the pyruvate dehydrogenase step, the ATP/ADP ratio and the levels of CoAsAc, oxaloacetate and isocitrate in the Krebs cycle.
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PMID:[Mechanisms of the regulation of muscle energy metabolism on oxidation of glucose and fatty acids. A mathematical model]. 621 68

Enhanced cardiac contractile function during the early post-birth period is a mammalian characteristic; however, concurrent metabolic measurements have not been systematically carried out. To define heart postnatal development, left ventricular pressure and rate of left ventricular pressure development (dP/dt) were measured in rats at 3, 5, 7, and 9 weeks post birth. When functional measurements were completed, the heart was excised, weighed, and tissue samples were used for chemical and/or enzymatic analyses. Left ventricular weight increased approximately 5-fold over the period studied, but was outstripped by 8-fold increases in body weight. Left ventricular DNA content increased dramatically between 3 weeks and 7 weeks post birth, then stabilized between 7 and 9 weeks post birth. Minor fluctuations in phosphofructokinase and lactate dehydrogenase enzyme activities suggest that glycolytic and anaerobic metabolisms undergo relatively small alterations as normal growth and development transpire. In contrast, enzymatic indices of aerobic metabolism (citrate synthase and malate dehydrogenase) were augmented approximately 6-fold without significant change in specific enzyme activity in purified mitochondria. Thus, mitochondria accumulated more rapidly than left ventricular tissue during heart growth. Magnesium-stimulated, myofibrillar ATPase enzyme activity approximately doubled over the intervening time between 3 weeks and 9 weeks post birth. Heart contractile function is augmented during normal growth roughly in parallel with increases in cell numbers, mitochondrial mass, and myofibrillar ATPase activity.
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PMID:Metabolic and contractile function enhancement during rat heart postnatal development. 623 38


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