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)

To investigate the pathogenesis of retina lesions caused by intraocular pressure elevation, activities and distribution of enzymes in retina including lactic dehydrogenase (LDH), succinate dehydrogenase (SDH), adenosinetriphosphatase (AT-Pase), acid phosphatase (ACP), cholinesterase (ChE), cytochrome oxidase (CCO), nucleotidase (5'-Nase) and glucose-6-phosphatase (G6Pase) were determined histochemically in 30 rabbits. It was found that 1) in the early stage of intraocular pressure elevation, the activities of LDH, SDH, ATPase, ACP, and ChE in retina were increased, while the activities of CCO, 5'-Nase decreased; 2) in the late stage of intraocular pressure elevation, the activities of all these enzymes but ACP, which showed a reduced activity, were close to the normal level; 3) in superoxide dismutase.(SOD-CCE) treated group, except the slight increase of LDH and G6Pase activities, the activities of the remaining enzymes were near to normal. Our results suggest that the various histochemical changes in retina induced by intraocular pressure elevation were compensatory in the early stage and were beneficial to the supply of energy needed in retinal tissue and cellular metabolism; while in the late stage, the lesion of retina cells developed due to decompensation. SOD-CCE could alleviate the retinal lesions caused by intraocular pressure elevation, and can be used as auxiliary drug for the treatment of intraocular pressure elevation.
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PMID:Enzymatic histochemistry of retina with experimental intraocular pressure elevation in rabbits. 873 48

Recovery of cell volume in response to osmotic stress is mediated in part by increases in the Cl- permeability of the plasma membrane. These studies evaluate the hypothesis that ATP release and autocrine stimulation of purinergic (P2) receptors couple increases in cell volume to opening of Cl- channels. In HTC rat hepatoma cells, swelling induced by hypotonic exposure increased membrane Cl- current density to 44.8 +/- 7.1 pA/pF at -80 mV. Both the rate of volume recovery and the increase in Cl- permeability were inhibited in the presence of the ATP hydrolase apyrase (3 units/ml) or by exposure to the P2 receptor blockers suramin and Reactive Blue 2 (10-100 microM). Cell swelling also stimulated release of ATP. Hypotonic exposure increased the concentration of ATP in the effluent of perfused cells by 170 +/- 36 nM in the presence of a nucleotidase inhibitor (P < 0.01). In whole-cell recordings with ATP as the charge carrier, cell swelling increased membrane current density approximately 30-fold to 16.5 +/- 10.4 pA/pF. These findings indicate that increases in cell volume lead to efflux of ATP through opening of a conductive pathway consistent with a channel, and that extracellular ATP is required for recovery from swelling. ATP may function as an autocrine factor that couples increases in cell volume to opening of Cl- channels through stimulation of P2 receptors.
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PMID:Autocrine signaling through ATP release represents a novel mechanism for cell volume regulation. 887 55

Salt tolerance of crops could be improved by genetic engineering if basic questions on mechanisms of salt toxicity and defense responses could be solved at the molecular level. Mutant plants accumulating proline and transgenic plants engineered to accumulate mannitol or fructans exhibit improved salt tolerance. A target of salt toxicity has been identified in Saccharomyces cerevisiae: it is a sodium-sensitive nucleotidase involved in sulfate activation and encoded by the HAL2 gene. The major sodium-extrusion system of S. cerevisiae is a P-ATPase encoded by the ENA1 gene. The regulatory system of ENA1 expression includes the protein phosphatase calcineurin and the product of the HAL3 gene. In Escherichia coli, the Na(+)-H+ antiporter encoded by the nhaA gene is essential for salt tolerance. No sodium transport system has been identified at the molecular level in plants. Ion transport at the vacuole is of crucial importance for salt accumulation in this compartment, a conspicuous feature of halophytic plants. The primary sensors of osmotic stress have been identified only in E. coli. In S. cerevisiae, a protein kinase cascade (the HOG pathway) mediates the osmotic induction of many, but not all, stress-responsive genes. In plants, the hormone abscisic acid mediates many stress responses and both a protein phosphatase and a transcription factor (encoded by the ABI1 and ABI3 genes, respectively) participate in its action.
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PMID:Salt tolerance in plants and microorganisms: toxicity targets and defense responses. 890 Sep 56

The 26 S proteasome can be assembled from the multicatalytic protease (or 20 S proteasome) and a large multisubunit regulatory complex in an ATP-dependent reaction. The 26 S proteasome and its regulatory complex were purified from rabbit reticulocytes for characterization of their nucleotidase properties. Both particles hydrolyze ATP, CTP, GTP, and UTP to the corresponding nucleoside diphosphate and inorganic phosphate. The Km values for hydrolysis of specific nucleotides by the 26 S proteasome are 15 microM for ATP and CTP, 50 microM for GTP, and 100 microM for UTP; Km values for nucleotide hydrolysis by the regulatory complex are 2-4-fold higher for each nucleotide. Several ATPase inhibitors (erythro-9-[3-(2-hydroxynonyl)]adenine, oligomycin, ouabain, and thapsigargin) had no effect on ATP hydrolysis by either complex whereas known inhibitors of proteolysis by the 26 S enzyme (hemin, N-ethylmaleimide (NEM), and vanadate) significantly reduced ATP hydrolysis by both particles. Hydrolysis of all nucleotides was inhibited by 5 mM NEM but only GTP and UTP hydrolysis was significantly reduced at 50 microM NEM. The 15 microM Km for ATP hydrolysis by the 26 S proteasome is virtually identical to the observed Km of 12 microM ATP for Ub-conjugate degradation. Although nucleotide hydrolysis is required for protein degradation by the 26 S proteasome, nucleotide hydrolysis and peptide bond cleavage are not strictly coupled. Substrate specificity constants (kcat/Km) are similar for hydrolysis of each nucleotide, yet GTP and UTP barely supported Ub-conjugate degradation. Further evidence that nucleotide hydrolysis is not coupled to peptide bond cleavage was obtained using N-acetyl-leucyl-leucyl-norleucinal (LLnL). This compound inhibited peptide hydrolysis by the multicatalytic protease and Ub-conjugate degradation by the 26 S proteasome, but it had little effect on ATP or UTP hydrolysis by the 26 S enzyme.
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PMID:Nucleotidase activities of the 26 S proteasome and its regulatory complex. 895 78

The pregnant rats were treated with formaldehyde (0.5 mg/kg daily per os) during whole period of pregnancy. The activity of cytochrome-c-oxidase, malate dehydrogenase, nucleotidase, glucose-6-phosphatase, beta-glucuronidase, N-acetyl-beta-glucosaminidase, beta-galactosidase, H(+)-ATPase, glutamate dehydrogenase, NAD- and NADP-isocitrate dehydrogenase, fructose-bisphosphate aldolase, glucose-6-phosphate dehydrogenase and content of protein in liver celts of offsprings (newborns, 2 weeks age and 2 months age) were studied. It was shown differences in development enzyme systems of control and experimental animals during ontogenesis.
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PMID:[Experimental study of the effect of formaldehyde during embryogenesis on the activity of rat liver enzyme systems in ontogenesis]. 913 53

We have cloned and expressed the yeast DNA helicase A in Escherichia coli at a high level (approximately 30 mg/L of culture) in soluble form. We describe here a simple two-step purification protocol that produces reasonable quantities of homogeneous enzyme. In denaturing gel electrophoresis the enzyme behaved as a approximately 90 kDa protein. The native structure, determined by gel-filtration studies, appeared to be hexameric and its quaternary structure was salt (NaCl) dependent. In low-salt buffers (containing 50 mM NaCl), the enzyme eluted in a single activity peak at an elution volume that appeared to correlate with a possible hexameric structure. In higher salt buffer (containing greater than 150 mM NaCl), the enzyme eluted as smaller assemblies (monomer/dimer). The recombinant helicase A was able to hydrolyze ATP or dATP with equal efficiency. The ATPase activity of the enzyme was absolutely DNA-dependent. The nucleotidase activities were comparable to those of the native enzyme. Kinetic analysis of the ATPase activity demonstrated that the Km of the enzyme was approximately 90 microM and the rate of ATP hydrolysis was approximately 20 ATP s-1 molecule-1. DNA sequences containing pyrimidine stretches were more effective activators than those containing purine stretches. However, poly(dC) appeared to be the most effective activator of the ATPase activity. The ATPase activity was inhibited by salt (NaCl) above 50 mM with a half-maximal inhibition at approximately 110 mM. It is likely that the active state of helicase A is hexameric. The helicase activity of the recombinant enzyme was stimulated significantly by the yeast replication protein A (RPA) and to a lower extent by the single-stranded DNA binding protein of E. coli (SSB). The DNA helicase migrated on a DNA template in a 5' --> 3' direction. Helicase A appeared to share a number of enzymatic characteristics including directionality, stimulation by RPA/SSB, and quaternary structure (monomer-hexamer) dynamics that are common to known replicative helicases such as DnaB helicase and the SV40 T-antigen.
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PMID:Yeast DNA helicase A: cloning, expression, purification, and enzymatic characterization. 934 Dec 18

Few studies have examined tubular function after subtotal nephrectomy (Nx) and conservative treatments. The effects of 70% and 80% Nx (associated with dietary phosphate restriction in the latter case) on the apical brush border membrane (BBM) enzymes 5'-nucleotidase, gamma glutamyl-transferase and alkaline-phosphatase, and one BBM Na-phosphate cotransporter (NaPi-2) were studied in rats after a six week period. Changes in activity and mRNA abundance of the BBM enzymes and in NaPi-2 protein and mRNA abundance were compared with changes in the distal markers of Na,K-ATPase activity and epidermal growth factor (EGF) production. The activity, but not the mRNA of BBM enzymes, was moderately reduced by the 70% Nx. Both the mRNA and activity of gamma glutamyl-transferase and alkaline-phosphatase were decreased in the 80% Nx, and the NaPi-2 mRNA, protein and Na,K-ATPase activities were also reduced. These effects (except for 5'nucleotidase and Na,K-ATPase) were partly reversed by phosphate restriction. Overproduction of EGF occurred after the 70% Nx, was blunted in the 80% Nx, and then partially restored by phosphate restriction. Aggravation of tubular alteration was associated with enhanced renal hyperplasia (increased DNA mass), reduced GFR and hyperphosphatemia, and high PTH levels, but reduced cAMP excretion. Improvement following phosphate restriction was associated with reduced hyperplasia and lowering of phosphatemia and PTH levels. These data demonstrate that Nx selectively affected BBM function through transcriptional changes that were partially reversed by phosphate restriction. Regulatory factors involved in these changes may include intracellular phosphate content and growth factors, but not the PTH effects that are impaired in chronic renal failure.
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PMID:Subtotal nephrectomy alters tubular function: effect of phosphorus restriction. 940

The effect of chronic aluminium exposure (25 mg/kg b.wt.) was studied on the lipid composition and various membrane-bound enzymes in different regions of monkey brain. Aluminium (Al) administration caused a significant decrease in the total lipid, glycolipid, and phospholipid content of primate brain. Cholesterol levels and the phospholipid to cholesterol ratio were, however, markedly increased as a consequence of Al administration, thereby indicating a loss of membrane integrity. This was further confirmed when Al treatment was found to have a significant effect on the various membrane-bound enzymes in terms of decreased activities of Na+ K+ ATPase and acetylcholinesterase, along with a decrease in the activity of the myelin-specific enzyme, 2' 3'-cyclic nucleotide phosphohydrolase.
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PMID:Alterations in lipid composition and neuronal injury in primates following chronic aluminium exposure. 952 55

The time and dose-dependent effects of the in vivo administration of hexachlorobenzene (HCB), on hepatic microsomal membrane functions, were studied in female Wistar rats. Administration of HCB (100 mg/100 g b.w.) resulted in time-dependent decreases in the activity of two membrane-bound enzymes: 5'nucleotidase and Na+/K+ ATPase. HCB was found to cause a significant rise in protein tyrosine kinase (PTK) activity during the early stages of intoxication (day 2), followed by a significant decrease at 10 days, returning to control levels after 20 days of treatment. A stimulatory effect of HCB on in vitro endogenous microsomal protein phosphorylation was observed from 2 days of intoxication up to 30 days of treatment, with an important stimulation of phosphorylation at 5 days. Administration of HCB (100 mg/100 g b.w.) for 10 days caused a 50% reduction in epidermal growth factor receptor (EGF-R) ligand binding. The effects of known specific inhibitors of protein phosphatases on endogenous protein phosphorylation were studied. HCB affected the labelling of several bands, as well as the 5'nucleotidase and PTK activities, in a dose-dependent manner. In conclusion, this study indicated that the in vivo administration of HCB results in a significant alteration of membrane function.
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PMID:Hexachlorobenzene-induced alterations of rat hepatic microsomal membrane function. 957 Mar 24

Excessive platelet accumulation and recruitment, leading to vessel occlusion at sites of vascular injury, present major therapeutic challenges in cardiovascular medicine. Endothelial cell CD39, an ecto-enzyme with ADPase and ATPase activities, rapidly metabolizes ATP and ADP released from activated platelets, thereby abolishing recruitment. Therefore, a soluble form of CD39, retaining nucleotidase activities, would constitute a novel antithrombotic agent. We designed a recombinant, soluble form of human CD39, and isolated it from conditioned media from transiently transfected COS-1 cells and from stably transfected Chinese hamster ovary (CHO) cells. Conditioned medium from CHO cells grown under serum-free conditions was subjected to anti-CD39 immunoaffinity column chromatography, yielding a single approximately 66-kD protein with ATPase and ADPase activities. Purified soluble CD39 blocked ADP-induced platelet aggregation in vitro, and inhibited collagen-induced platelet reactivity. Kinetic analyses indicated that, while soluble CD39 had a Km for ADP of 5.9 microM and for ATP of 2.1 microM, the specificity constant kcat/Km was the same for both substrates. Intravenously administered soluble CD39 remained active in mice for an extended period of time, with an elimination phase half-life of almost 2 d. The data indicate that soluble CD39 is a potential therapeutic agent for inhibition of platelet-mediated thrombotic diatheses.
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PMID:Inhibition of platelet function by recombinant soluble ecto-ADPase/CD39. 957 48


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