Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have shown that the rat liver plasma membrane has at least two (Ca2+-Mg2+)-ATPases. One of them has the properties of a plasma membrane Ca2+-pump (Lin, S.-H. (1985) J. Biol. Chem. 260, 7850-7856); the other one, which we have purified (Lin, S.-H., and Fain, J.N. (1984) J. Biol. Chem. 259, 3016-3020) and characterized (Lin, S.-H. (1985) J. Biol. Chem. 260, 10976-10980) has no established function. In this study we present evidence that the purified (Ca2+-Mg2+)-ATPase is a plasma membrane ecto-ATPase. In hepatocytes in primary culture, we can detect Ca2+-ATPase and Mg2+-ATPase activities by addition of ATP to the intact cells. The external localization of the active site of the ATPase was confirmed by the observation that the Ca2+-ATPase and Mg2+-ATPase activities were the same for intact cells, saponin-treated cells, and cell homogenates. Less than 14% of total intracellular lactate dehydrogenase, a cytosolic enzyme, was released during a 30-min incubation of the hepatocytes with 2 mM ATP. This indicates that the hepatocytes maintained cytoplasmic membrane integrity during the 30-min incubation with ATP, and the Ca2+-ATPase and Mg2+-ATPase activity measured in the intact cell preparation was due to cell surface ATPase activity. The possibility that the ecto-Ca2+-ATPase and Mg2+-ATPase may be the same protein as the previously purified (Ca2+-Mg2+)-ATPase was tested by comparing the properties of the ecto-ATPase with those of (Ca2+-Mg2+)-ATPase. Both the ecto-ATPase and the (Ca2+-Mg2+)-ATPase have broad nucleotide-hydrolyzing activity, i.e. they both hydrolyze ATP, GTP, UTP, CTP, ADP, and GDP to a similar extent. The effect of Ca2+ and Mg2+ on the ecto-ATPase activity is not additive indicating that both Ca2+- and Mg2+-ATPase activities are part of the same enzyme. The ecto-ATPase activity, like the (Ca2+-Mg2+)-ATPase, is not sensitive to oligomycin, vanadate, N-ethylmaleimide and p-chloromercuribenzoate; and both the ecto-ATPase and purified (Ca2+-Mg2+)-ATPase activities are insensitive to protease treatments. These properties indicate that the previously purified (Ca2+-Mg2+)-ATPase is an ecto-ATPase and may function in regulating the effect of ATP and ADP on hepatocyte Ca2+ mobilization (Charest, R., Blackmore, P.F., and Exton, J.H. (1985) J. Biol. Chem. 260, 15789-15794).
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PMID:Two Ca2+-dependent ATPases in rat liver plasma membrane. The previously purified (Ca2+-Mg2+)-ATPase is not a Ca2+-pump but an ecto-ATPase. 245 81

The changes in conformation of F-actin induced by the binding of the glycolytic enzyme lactate dehydrogenase were studied in myosin-free single ghost muscle fibres. The formation of the lactate dehydrogenase-F-actin complex was accompanied by changes in the parameters of intrinsic (tryptophan) and extrinsic (rhodaminyl-phalloin) polarized fluorescence of ghost muscle fibre F-actin. Lactate dehydrogenase stimulated actin-activated Mg2+-ATPase of myosin subfragment 1 by 30%. F-actin of ghost fibres depressed lactate dehydrogenase activity to 20% of the initial values. It is suggested that the energy-providing mechanism is coupled with that of muscle contraction through conformational changes in F-actin.
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PMID:Lactate dehydrogenase-induced conformational changes of F-actin in myosin-free ghost single fibres. 253 93

1. We performed an enzymatic characterization of two different fractionation procedures of ventricles from rat hearts. The enzymatic assays covered succinic dehydrogenase as a marker for inner mitochondrial membranes, monoamine oxidase as a marker for outer mitochondrial membranes, NADPH-cytochrome c reductase and RNA as endoplasmatic reticular markers, acid phosphatase as a lysosomal marker, and lactic dehydrogenase as a marker for the "soluble" compartment; DNA was estimated for nuclear contamination. 2. The plasma membrane markers 5'-nucleotidase, Ca2+-ATPase, Mg2+-ATPase, Na+-K+-ATPase, and adenylate cyclase were determined. 3. The roughly prepared membrane fractions showed increased yields of the membrane markers; the number of beta receptors, determined with (-)-[3H] dihydroalprenolol and DL-propranolol, amounted to 68 +/- 6 fmol/mg protein (KD = 3390 +/- 450 pmol, Hill coefficient = 1.5). 4. The membrane fraction prepared with a linear sucrose gradient showed an increased inner mitochondrial membrane marker; presumably the outer mitochondrial membrane was stripped off. The beta-receptor number was 39 +/- 3 fmol/mg protein (KD = 6250 +/- 300 pmol; Hill coefficient = 1.2).
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PMID:Beta-adrenergic receptors and enzymes in rat myocardial membranes: implications of fractionation procedures and beta-adrenoceptor antagonists. 284 52

A study was made of changes in F-actin conformation occurring in a myosin-free single ghost fibre induced by the binding of glycolytic enzyme lactate dehydrogenase (LDG) to F-actin. The formation of the complex between LDG and F-actin induces changes in the parameters of the intrinsic (tryptophan) and extrinsic (rodominil--phalloin) polarized fluorescence of F-actin of the ghost muscle fibre. It is found that LDG stimulates Mg2+-ATPase of actomyosin in solution. It is assumed that the coupling of energy-providing mechanism with that of muscle contraction may be accomplished through the conformation changes in F-actin.
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PMID:[Interaction of the enzymes of cellular energy support with the F-actin of the thin filaments of muscle fiber. I. The binding of lactate dehydrogenase with F-actin induces changes in the structural state of the components of the complex]. 297 67

Intact synaptosomes isolated from the electric organ of the electric ray Torpedo marmorata contain, at their surface, enzyme activities for the hydrolysis of externally applied nucleoside phosphates. The diazonium salt of sulfanilic acid, as a low-molecular-weight, slowly permeating, covalent inhibitory agent, selectively blocks these enzyme activities and leaves intracellular lactate dehydrogenase intact. The ectoenzymes comprise both a nucleoside triphosphate and diphosphate phosphohydrolase, as well as a 5'-nucleotidase. Activity of nonspecific ectophosphatases is absent. The nucleoside triphosphatase hydrolyzes almost equally well ATP, GTP, CTP, UTP, and ITP and is activated to a similar degree by Mg2+ or Ca2+. It has a high affinity for ATP (Km for ATP in the presence of Mg2+, 75 microM; in the presence of Ca2+, 66 microM). Maximal rates in the presence of Mg2+ and Ca2+ were very similar (34.8 and 32.5 nmol of Pi/min/mg of synaptosomal protein, respectively). Either Mg-ATP or Ca-ATP can act as a true substrate. ADP inhibits hydrolysis of ATP, but AMP is without effect. The nucleoside triphosphatase is not inhibited significantly by a number of inhibitors of mitochondrial Mg2+-ATPase or of Ca2+ + Mg2+-ATPases. It is, however, considerably inhibited by filipin and quercitin. The capacity of intact synaptosomes to hydrolyze also extracellular ADP, GDP, AMP, GMP, and IMP suggests that the nucleoside triphosphatase is part of an enzyme chain that causes complete hydrolysis of the respective nucleoside triphosphate to the nucleoside. We conclude that the cholinergic nerve terminals of the Torpedo electric organ can hydrolyze ATP released on coexocytosis with acetylcholine via an ectonucleoside triphosphatase activity that is different from known endogenous nerve terminal ATPases. The final product of the hydrolysis, adenosine, can then be salvaged by the nerve terminal for resynthesis of ATP. Other possible physiological functions of the ectonucleotidases are discussed.
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PMID:Ectonucleotidase activities associated with cholinergic synaptosomes isolated from Torpedo electric organ. 301 88

The outer and inner bilayers of the apical membrane complex of Schistosoma mansoni were sequentially stripped from adult worms by two incubations in 0.1% digitonin solutions. Membrane removal was evaluated by electron microscopy of worms and bilayer material, using Con A-ferritin as a marker for the outer bilayer. Amounts of Con A removed by the digests were measured with a tritiated Con A marker. To measure the purity of the fractions membrane markers were characterised and quantitated for both bilayers. In the absence of the usual enzymatic markers for plasma membrane diazotised [125I]-iodosulfanilic acid was used as a marker for the outer bilayer. Alkaline phosphatase and a Na+, Mg2+-ATPase were localised to the inner bilayer. From these results we can deduce that the inner bilayer is analogous to the typical, apical plasma membrane of other animal epithelia. The outer bilayer does not share these enzymatic similarities. The integrity of the syncytium after removal of the outer bilayer and the increased levels of lactate dehydrogenase in the supernatant after removal of the inner bilayer suggests that the outer bilayer is secondary in maintaining the permeability barrier of the apical membrane complex, with respect to soluble proteins. The possible significance of these results in terms of the destructive action of complement on the parasite are discussed.
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PMID:Sequential removal of outer bilayer and apical plasma membrane from the surface epithelial syncytium of Schistosoma mansoni. 685 11

The effect of a single oral dose of malathion (1 g/kg body wt.) on the digestive and absorptive functions of the intestinal epithelium has been investigated in rats. The absorption of glucose and glycine was considerably reduced (35%) inpesticide fed animals compared to controls. The activities of brush border sucrase, lactase, alkaline phosphatase, Mg2+-ATPase and lactate dehydrogenase were also significantly depressed in malathion exposed rats, but there was no change in the leucine aminopeptidase levels under these conditions. Mucosal DNA, RNA and protein contents remained unaltered in pesticide toxicity. These results suggest that malathion toxicity induces functional derangements of the intestine.
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PMID:Effect of a single oral dose of malathion on D-glucose and glycine uptake and on brush border enzymes in rat intestine. 744 81

Adriamycin, which is widely used in the treatment of various neoplastic conditions, exerts toxic effects in several organs. Adriamycin nephrotoxicity has been recently documented in a variety of animal species. The present study was designed to investigate the effect of lipoic acid on the nephrotoxic potential of adriamycin. The study was carried out with adult male albino rats of Wistar strain. Test animals were divided into four groups of six rats each as follows: Group I (control) received only normal saline throughout the course of the experiment. Group II (ADR) received intravenous injections of adriamycin through the tail vein (1 mg kg(-1) body wt day(-1)) once a week for a period of 12 weeks. Group III (LA) received lipoic acid (35 mg kg(-1) body wt day(-1)) intraperitoneally once a week for a period of 12 weeks. Group IV (ADR + LA) received a single injection of lipoic acid intraperitoneally 24 h prior to the administration of adriamycin through the tail vein once a week for a period of 12 weeks. Intravenous injections of adriamycin resulted in decreased activities of the glycolytic enzymes; hexokinase, phosphoglucoisomerase, aldolase and lactate dehydrogenase in the rat renal tissue. The gluconeogenic enzymes, glucose-6-phosphatase and fructose-1,6-diphosphatase, showed a decline in their activities on adriamycin administration. The transmembrane enzymes namely the Na+,K+-ATPase, Ca2+-ATPase, Mg2+-ATPase and the brush-border enzyme alkaline phosphatase also showed a decrease in their activities. This decrease in the activities of ATPases and alkaline phosphatase suggests basolateral and brush-border membrane damage. Decreased activities of the TCA cycle enzymes isocitrate dehydrogenase, succinate dehydrogenase and malate dehydrogenase, suggest a loss in mitochondrial function and integrity. Nephrotoxicity was evident from the increased excretions of N-acetyl-beta-D-glucosaminidase and gamma-glutamyl transferase in the urine of adriamycin administered rats. These biochemical disturbances were effectively counteracted on pre-treatment with lipoic acid, which brought about an increase in the activities of glycolytic enzymes, ATPases and the TCA cycle enzymes. On the other hand, the gluconeogenic enzymes showed a further decrease in their activities on lipoic acid pretreatment. LA pretreatment also restored the activities of the urinary enzymes to normal. These observations shed light on the nephroprotective action of lipoic acid rendered against experimental aminoglycoside toxicity.
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PMID:The influence of lipoic acid on adriamycin induced nephrotoxicity in rats. 1284 26

Farnesoid X receptor (FXR) is a bile acid-activated transcription factor that is a member of the nuclear hormone receptor superfamily. Fxr-null mice exhibit a phenotype similar to Byler disease, an inherited cholestatic liver disorder. In the liver, activation of FXR induces transcription of transporter genes involved in promoting bile acid clearance and represses genes involved in bile acid biosynthesis. We investigated whether the synthetic FXR agonist GW4064 could protect against cholestatic liver damage in rat models of extrahepatic and intrahepatic cholestasis. In the bile duct-ligation and alpha-naphthylisothiocyanate models of cholestasis, GW4064 treatment resulted in significant reductions in serum alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase, as well as other markers of liver damage. Rats that received GW4064 treatment also had decreased incidence and extent of necrosis, decreased inflammatory cell infiltration, and decreased bile duct proliferation. Analysis of gene expression in livers from GW4064-treated cholestatic rats revealed decreased expression of bile acid biosynthetic genes and increased expression of genes involved in bile acid transport, including the phospholipid flippase MDR2. The hepatoprotection seen in these animal models by the synthetic FXR agonist suggests FXR agonists may be useful in the treatment of cholestatic liver disease.
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PMID:Hepatoprotection by the farnesoid X receptor agonist GW4064 in rat models of intra- and extrahepatic cholestasis. 1523 10

Brief episodes of myocardial ischemia-reperfusion (IR) employed during reperfusion after a prolonged ischemic insult may attenuate the total ischemia-reperfusion injury. This phenomenon has been termed ischemic postconditioning. In the present study, we studied the possible effect of ischemic postconditioning on an ischemic reperfusion (IR)-induced myocardium oxidative injury in rat model. Results showed that ischemic postconditioning could improve arrhythmia cordis, reduce myocardium infarction and serum creatin kinase (CK), lactate dehydrogenase (LDH) and aspartate transaminase (AST) activities in IR rats. In addition, ischemic postconditioning could still decrease myocardium malondialdehyde (MDA) level, and increased myocardium Na+-K+-ATPase, Ca2+-Mg2+-ATPase, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) activities. It can be concluded that ischemic postconditioning possesses strong protective effects against ischemia reperfusion-induced myocardium oxidative injury in IR rats.
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PMID:Protective effect of ischemic postconditioning against ischemia reperfusion-induced myocardium oxidative injury in IR rats. 2245 31


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