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)

The goal was to describe the metabolic profile of ganglionic and cortical arteries and arterioles in aging normotensive male rats. Five enzymes indicative of key metabolic pathways in the vessel walls were semiquantitatively evaluated using bright-field histochemical microscopy. Lactate dehydrogenase showed significant reactivity which increased with vessel diameter in cortical and ganglionic vessels in all age groups tested. Succinate dehydrogenase and cytochrome oxidase showed little reactivity in both cortical and ganglionic vessels, suggesting a reduced role for aerobic metabolic pathways. Myosin ATPase reactivity was high in cortical and ganglionic vessels. Only this enzyme showed an increased reactivity that was correlated with the age and diameter of the vessel. Glucose-6-phosphate dehydrogenase reactivity was more pronounced in cortical than ganglionic vessels, suggesting that the hexose-monophosphate-shunt may be more active in the cortical vessels. There were no regional differences in enzyme reactivity throughout the caudatoputamen. In conclusion, both the cortical and ganglionic vessels are metabolically active, with significant anaerobic glycolysis, and reduced, but observable capacity for aerobic metabolism. The decreased myosin ATPase reactivity and the low level of glucose-6-phosphate dehydrogenase reactivity in the ganglionic arterioles of senescent rats may contribute to the susceptibility of these vessels to cerebrovascular accidents.
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PMID:A histochemical study of cerebral cortical vessels and ganglionic vessels of the caudatoputamen in aging normotensive rats. 315 35

The role of reduced glutathione (GSH) in lens membrane function was studied by depleting GSH with 1-chloro-2,4-dinitrobenzene (CDNB), a reaction catalyzed by GSH-S-transferase. Depletion of GSH in the lens epithelium by 70-90% led to a decrease in uptake and increase in efflux of 86Rb. ATP levels and Na+/K+-ATPase activity were normal while there was a slight decrease in lactate production. The results provide the first direct evidence that depletion of endogenous GSH per se does not lead to inactivation of Na+/K+-ATPase. However, lenses deficient in GSH when challenged with a normally tolerated level of H2O2 showed significant inactivation of membrane ATPase without a further increase in membrane permeability. Pretreatment with CDNB resulted in a 3-fold stimulation of the hexose monophosphate shunt activity which is attributed to the unexpected finding of a significant increase in the level of oxidized glutathione in the lens. It is concluded that deficiency of GSH causes a marked increase in membrane permeability and such lenses are susceptible to oxidative damage resulting in inactivation of the Na+/K+ pump, thus leading to ionic changes and cataract development.
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PMID:Effect of glutathione depletion on cation transport and metabolism in the rabbit lens. 318 92

1. The glial blood-brain barrier of invertebrates is an accessible, polarised glial layer that permits study of glial cells in their normal relations with neurons. Crayfish 2. The glial "perineurium" forms the blood-brain interface in crayfish, and acts as a barrier to horseradish peroxidase (HRP) and ionic lanthanum. By contrast, the perineurium of the peripheral nervous system is relatively permeable. 3. The ionic permeability of the blood-brain interface can be studied in a sucrose gap chamber, using an extra-cellular microelectrode to monitor the potential across the perineurium following changes in the bathing medium. Subtraction of the microelectrode trace from the sucrose gap records gives the change in the axonal membrane potential. 4. Raised [K+] in the bath causes a complex change in perineurial potential, with the initial transient indicating that the outer (basal) glial membrane is highly K+ selective. The axonal response shows that the time constant for K+ uptake (tau u) and efflux (tau E) across the perineurium of the order of 3-4 min, but the interstitial [K+] in the steady state, [K+] infinity is always less than in the bathing medium. The results are explained by a model incorporating a K+ sink, which may be glial. 5. Strophanthidin and ethacrynic acid have little effect on tau u or K infinity, but cause a rise of tau E. Cold temperature pulses causes changes in the perineurial potential compatible with depolarisation of the inner (apical) membrane. A model is proposed with a Na+-K+-2 Cl co-transporter on the perineurial basal membrane, and an electrogenic Na+-K+-ATPase on the apical.membrane, consistent with results from vertebrate glial/ependymal epithelia. Cephalopods 6. The brain of the cuttlefish Sepia has an extensive system of microvessels. In the vertical and optic lobes studied, a perivascular glial layer forms a barrier to HRP. The occluding structure appears not to be a classical tight junction but may involve condensation of extracellular material. There is no barrier between retinal axons and blood. 7. Studies with radiolabelled polyethylene glycol (PEG4000) and EDTA show that the Sepia blood-brain barrier is as tight as the endothelial barrier of mammals. 8. A modification of the Oldendorf arterial injection technique is used to show that glucose transport at the Sepia barrier is mediated by a Na+-independent hexose carrier resembling that of mammalian red cells and blood-brain barrier. 9. The blood-axon interface fo mantle nerves in the squid Alloteuthis is relatively impermeable to small ions.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:The glial blood-brain barrier of crustacea and cephalopods: a review. 333 91

Changes in carbohydrate metabolism were studied in midgut gland, muscle, and gill tissues of marine prawn Penaeus indicus exposed to a sublethal concentration (0.3 ppm) of phosphamidon. A significant decrease in glycogen and pyruvate and an increase in lactate content were observed in all phosphamidon-exposed prawn tissues after 96 hr. An increase in phosphorylase a and aldolase activity levels suggested the increased formation of triose sugars during phosphamidon toxicity. LDH activity was considerably decreased and an increment in lactate content was observed which indicates reduced mobilization of pyruvate into the citric acid cycle. Glucose-6-phosphate dehydrogenase activity was considerably increased, suggesting the enhanced oxidation of glucose in the hexose monophosphate shunt pathway. Krebs cycle enzymes such as NAD-isocitrate dehydrogenase, succinate dehydrogenase, and malate dehydrogenase were found to be decreased, suggesting the impairment in mitochondrial oxidative metabolism due to the acute toxic impact of phosphamidon. Cytochrome-c oxidase and Mg2+ ATPase activity levels were also decreased considerably, suggesting impaired energy synthesis and breakdown during phosphamidon toxicity, as a result of reduced oxidation of glucose aerobically. The increase in acid and alkaline phosphatase activities indicates the enhanced breakdown of phosphate to release energy in view of inhibiton or impairment in the ATPase system during phosphamidon-induced stress. These results suggest that phosphamidon has a profound effect on the oxidative metabolism of prawn which results in the triggering of compensatory metabolic pathways for survivability.
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PMID:Modulation of carbohydrate metabolism in the selected tissues of marine prawn, Penaeus indicus (H. Milne Edwards), under phosphamidon-induced stress. 337 38

Mammalian skeletal muscles are composed of slow (type I) and fast (type II) twitch fibers, which, as reflected by their enzyme activity patterns, are characterized by specific metabolic properties. Type I fibers are always "oxidative" but nevertheless form a spectrum. Type II fibers likewise form a spectrum but display a wider range with "oxidative" and "glycolytic" extremes. As a result, type I and type II fibers can be classified independently of myofibrillar ATPase histochemistry by their specific enzyme activity profiles. In this context, activity ratios between enzymes of anaerobic and aerobic pathways can be used as discriminative parameters. Similarly, specific ratios of enzymes catalyzing unidirectional reactions in hexose metabolism (hexokinase, phosphofructokinase, fructose-1,6-bisphosphatase) separate the two fiber populations. The histochemically defined IIA and IIB subtypes cannot be separated into distinct metabolic groups. In view of the continuum of metabolic properties, skeletal muscle is an extremely heterogeneous tissue in which each fiber represents a separate metabolic compartment.
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PMID:Metabolic properties of muscle fibers. 353 89

We have reported [Saito, M., Saito, M., & Rosenberg, A. (1984) Biochemistry 23, 1043-1046] that the monovalent cationic ionophore monensin reduced the incorporation of labeled galactose into oligosaccharidyl glycosphingolipids (globotriaosylceramide, globotetraosylceramide, and gangliosides) and induced a cellular accumulation of glucosyl- and lactosylceramide in cultured diploid human fibroblasts. We have undertaken further studies on the effects of monensin and made comparison with the effects of related monovalent cation transporters on plasma membrane glycosphingolipid anabolism in human fibroblasts. Our results demonstrate that ionic flux can markedly influence glycosphingolipid synthesis, and they indicate that, like glycoprotein, the sites of glycosylation of the initial, precursor glycosphingolipids are different from the sites of higher glycosylation. At a concentration of 10(-7) M, monensin induced the maximum inhibition of incorporation of labeled galactose into polyglycosyl sphingolipids: globotriaosylceramide, globotetraosylceramide, and gangliosides; increased incorporation of labeled galactose into glucosyl- and lactosylceramide was clearly evident, and their content rose measurably in the cell at concentrations of monensin as low as 10(-8) M. These effects of monensin were reversible. Incorporation of labeled galactose into higher glycosylated neutral glycosphingolipids and gangliosides slowly resumed, and the accumulated glycosylceramide diminished after removal of monensin from the culture medium. Ouabain (plasma membrane Na+,K+-ATPase inhibitor) and A23187 (Ca2+ ionophore) also caused a rapid increase in incorporation of labeled hexose into glucosylceramide and decreased its incorporation into higher neutral glycosphingolipids and into gangliosides.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Influence of monovalent cation transport on anabolism of glycosphingolipids in cultured human fibroblasts. 401 85

The actively transported sugar D-glucose binds to brush borders disrupted with tris(hydroxymethyl)aminomethane in preference to D-mannose and L-glucose, which are not actively transported. This preferential binding of D-glucose is not dependent on either added Na(+) or adenosine triphosphatase activity stimulated by Na(+) with K(+) and Mg(2+), but it is temperature-dependent and is completely inhibited by 0.1 millimolar phlorizin and 1 millimolar mercuric chloride.
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PMID:D-glucose: preferential binding to brush borders disrupted with tris(hydroxymethyl)aminomethane. 601 48

A method has been developed for calculating rate constants for dehydration of aldehydes that induce ATPase reactions by kinases and where 18O is transferred from the aldehyde or its hydrate to inorganic phosphate during the reaction. The method involves measurement of the fraction of 18O in phosphate by 31P NMR after the ATPase reaction has proceeded for several minutes with zero-order kinetics. The reaction is started by addition of the aldehyde in a small volume of H2 18O, and the speed of washout of 18O by reversible dehydration relative to the rate of the ATPase reaction allows calculation of the rate constants if the hydration equilibrium constant is known from the proton NMR spectrum of the aldehyde. Dehydration rate constants (s-1 at pH 8-8.5, 0.1 M buffer, 25 degrees C) for the following aldehydes (all over 95% hydrated) and kinases used are as follows: D-glyceraldehyde with glycerokinase, 0.03; 2,5-anhydro-D-mannose 6-phosphate with fructose-6-phosphate kinase, 0.025; 2,5-anhydro-D-mannose or 2,5-anhydro-D-talose with fructokinase, 0.029 and 0.017, respectively; D-gluco-hexodialdose with hexokinase, 0.068. With betaine aldehyde and choline kinase or glyoxylate and pyruvate kinase, no 18O was transferred to phosphate during the ATPase reactions. However, the dehydration rate constant for glyoxylate (0.007 s-1 at pH 7 extrapolated to zero buffer concentration and up to 0.11 s-1 at pH 9.0 with 0.3 M buffer) was determined by extrapolating the initial rate of reduction of the free aldehyde catalyzed by lactate dehydrogenase to infinite enzyme levels.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A novel method for determining rate constants for dehydration of aldehyde hydrates. 609 90

Pyrophosphate, p-nitrophenyl phosphate and a variety of pyrimidine and purine nucleotides are hydrolyzed by the solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. The pH optima (or ranges) for hydrolysis of substrates are 8.0 (pyrophosphate), 8.8 (p-nitrophenyl phosphate), 8.4-8.9 (nucleoside monophosphates), and 7.1-8.1 (nucleoside triphosphates); all substrates, with the exception of nucleoside triphosphates, have a higher affinity for the solubilized enzyme at pH 7.4 than at their optimal pH for hydrolysis. ATP is degraded completely by the enzyme preparation to adenosine and inorganic phosphate, but since neither ADP nor ATP accumulate in the incubation medium it is not known whether ATP hydrolysis involves the sequential hydrolysis of terminal phosphate groups. Isoelectric focusing and various chromatographic procedures (gel permeation, ion-exchange and hydrophobic interaction chromatography) fail to separate the alkaline phosphatase, phosphodiesterase, 5'-nucleotidase, adenosine triphosphatase and ribonuclease activities associated with the solubilized membrane preparation. Additionally, inhibitor studies indicate that only a single enzyme with low substrate specificity is involved in the hydrolysis of nucleotides, p-nitrophenyl phosphate, pyrophosphate and hexose phosphate esters. Purines and pyrimidines and their nucleosides interact with the active site, and in some instances activity of the enzyme is stimulated by an unknown mechanism.
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PMID:Nucleotide hydrolysis by solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. 613 88

Male Wistar rats were exposed to 4 ppm NO2 for 10 days in order to examine the relationship between the changes in components of red cell membranes and alterations of erythrocyte population. Na+, K+-ATPase activity of red blood cell membranes of exposed animals showed a significantly higher value than that of the control at the first and fourth days of exposure and then decreased to under the control value at the seventh day. In order to examine changes in erythrocyte population, red blood cells were fractionated into four fractions according to their density using Dextran density centrifugation. The alteration of the percentage of lowest-density cells (fraction IV) of exposed animals was completely consistent with that of Na+,K+-ATPase activity in addition to that of the sialic acid content as described in a previous report (K. Kaya, T. Miura, and K. Kubota (1980). Environ. Res. 23, 397-409.). The percentage of fraction IV was 1.43- (P less than 0.05) and 1.68-fold (P less than 0.01) those of the control at the first and fourth days of exposure, respectively, and then decreased to under the control value at the seventh day. This decrease accompanied increases in the percentages of higher-density cells (fractions I and II). Examination of subfractions of red blood cells showed that Na+,K+-ATPase activity and the sialic acid content of three fractions with lower densities have higher values in exposed animals than in the control 1 day after exposure to NO2. Based on these results, it is concluded that increases in Na+,K+-ATPase activity and the sialic acid content occurring 1 day after exposure to 4 ppm NO2 were caused by elevated levels of these components in three fractions with lower densities as well as by an increase in the percentage of lowest-density cells in the erythrocyte population. It was also suggested that NO2 inhalation accelerated aging of erythrocytes with respect to density. The change in Ca2+,Mg2+-ATPase activity, in addition to that in the hexose content as described in a previous report (Kaya et al., 1980), was different from those in the sialic acid content and Na+,K+-ATPase activity. Ca2+,Mg2+-ATPase activity and the hexose content of exposed animals showed slightly reduced values 1 day after exposure to NO2. In all subfractions of red blood cells these values were slightly lower in exposed animals than in the controls. Therefore, reduction in Ca2+,Mg2+-ATPase activity and the hexose content is not due to changes in erythrocyte population.
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PMID:Effects of nitrogen dioxide on red blood cells of rats: alterations of cell membrane components and populational changes of red blood cells during in vivo exposure to NO2. 614 61


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