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

---

Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Data from the literature have demonstrated that synaptosomal preparations from various sources can hydrolyze externally added ATP. Various authors characterized this activity as an ecto-ATPase. In the present report, we demonstrate that synaptosomal preparations obtained from the cerebral cortex of rats show ATPase activity that could not be dissociated from ADPase activity, suggesting that an ATP-diphosphohydrolase is involved in ATP and ADP hydrolysis. Furthermore, the ATP and ADP hydrolysis could not be attributed to associations of enzymes that could mimic an ATP-diphosphohydrolase because none of the following activities were detected in our assay conditions inorganic pyrophosphatase, adenylate kinase, or nonspecific phosphatases. A possible association between an ATPase and an ADPase was excluded on the basis of both the kinetics and much additional data on inhibitors, ion dependence, pH, etc. The present results demonstrate that in synaptosomal preparations from cerebral cortex an ATP-diphosphohydrolase is involved, at least in part, in ATP and ADP hydrolysis.
...
PMID:Characterization of an ATP diphosphohydrolase (EC 3.6.1.5) in synaptosomes from cerebral cortex of adult rats. 183 6

1. Calcium-stimulated ATPase-ADPase activities were studied in a microsomal fraction of rat placental tissue. 2. The kinetic characteristics correspond to those of ATP-diphosphohydrolase, also known as apyrase (E.C. 3.6.1.5). 3. These characteristics include the lack of specificity towards nucleoside di- and triphosphates, activation by Ca2+, Mg2+ or Mn2+, insensitivity to specific inhibitors of some ATPase and absence of an effect of sulphydryl reagents. 4. Chemical modification of tyrosine, tryptophan, arginine and carboxylic residues decreases both ATPase and ADPase activities. 5. The substrate analogue, 5'-(beta, gamma-methylene)triphosphate, protected both enzyme activities against all the modifying amino acid reagents tested. 6. Placental fractions (homogenate and microsomes) inhibit ADP-dependent platelet aggregation. 7. The solubilized microsomal enzyme has a molecular mass of 67 kDa by size-exclusion chromatography; the pI is 9.36. 8. A differential effect is observed on the activation produced by Concanavalin A on microsomal and solubilized fractions when treated in the presence and absence of alpha-methylmannoside.
...
PMID:ATPase-ADPase activities of rat placental tissue. 183 61

In the present study, we examined the ontogeny of ATP and ADP hydrolysis by cerebral cortex synaptosomes from rats of various ages (0-, 7-, 14-, 21- and 60 to 90-day-old rats) in order to learn whether hydrolytic activity increases during the period of intense brain growth, as has been reported for other enzymes involved in neurotransmitter metabolism. The results demonstrate that ATP and ADP hydrolyzing activities increase in parallel from birth until the second postnatal week (about 4-fold), followed by a slight and statistically insignificant increase until the animal reaches adulthood. The maximum increase in nucleotide hydrolysis coincided with maximum brain growth, which may indicate a role for the enzyme in neurotransmission. Furthermore, the parallel development of both activities (ATPase and ADPase) strongly suggest that a single enzyme, an ATP diphosphohydrolase, is involved in ATP and ADP hydrolysis by the synaptosomal fraction.
...
PMID:Ontogeny of ATP and ADP hydrolysis by cerebral cortex synaptosomes from rats. 196 28

Dithiothreitol-dependent MgATP2- and Mg-ADP- hydrolytic activities owing to nucleoside triphosphate hydrolase were examined kinetically in tachyzoite cells of five strains of Toxoplasma gondii with various virulence. The tachyzoites of all the strains were revealed to have a high ATP and ADP hydrolytic potency. The value of Vmax and Km obtained from each strain indicated that there were two classified types of T. gondii about ATP and ADP hydrolysis. The most virulent strain (RH) and avirulent strain (Fukaya) were classified in a type with higher ATPase than ADPase activities. Two virulent strains (C56, Beverley) and an avirulent strain (ME49) were classified in the other type with the same activities of ATPase and ADPase.
...
PMID:Remarkable activities of nucleoside triphosphate hydrolase in the tachyzoites of both virulent and avirulent strains of Toxoplasma gondii. 214 44

Activation of the low affinity Ca-ATPase and Ca-ADPase by increasing concentrations of their cationic cofactor calcium (0.1-8.0 mmol.l-1) or by increasing concentration of substrates ATP or ADP (0.1-8.0 mmol.l-1) was influenced on similar mode by sodium azide. Kinetic analysis of the NaN3 induced inhibition, revealed that both enzyme activities are probably secured by the same system which is capable to hydrolyze ADP during the absence of ATP. A possible role for Ca-ADPase in controlling the calcium channel during ATP deficiency is discussed.
...
PMID:Ca-dependent ADPase--the possible regulator of calcium channel during the deficiency of ATP. 244 85

ATP diphosphohydrolase (EC 3.6.1.5) hydrolyzes pyrophosphate bonds of nucleoside di- and triphosphates in the presence of divalent cations. We purified the enzyme from the vessel wall of bovine aortas. The procedure gave a homogeneous preparation of ATP diphosphohydrolase for the first time from an animal source. Bovine aorta microsomes were treated with 50 mM bicarbonate buffer (pH 10.0) containing 0.025% Triton X-100. The enzyme was then solubilized from the microsomes with 0.5% Triton X-100 and purified to homogeneity by DEAE-Sepharose CL-6B chromatography and 5'AMP-Sepharose 4B affinity chromatography. The apparent molecular mass of the pure enzyme was 110 kDa. The activity recovered was 6% of that of the microsomes. The enzyme was more active with Ca2+ than Mg2+. The sensitivity of ADPase activity to divalent cations was higher than that of ATPase activity. The enzyme had broad substrate specificity to nucleoside di- and triphosphates.
...
PMID:Purification of ATP diphosphohydrolase from bovine aorta microsomes. 254 Sep 63

Biologically active concentrations of potently vasoactive and platelet-active adenine nucleotides are generated in plasma by a variety of pathophysiological mechanisms. Although there is evidence that ATP and ADP are inactivated by endothelial ectonucleotidases, there has been little attempt to study the metabolic routes of their catabolism in blood or to assess the contribution of this process to their clearance in vivo. Therefore, we have studied the rates and patterns of catabolism of ATP, ADP, and AMP in whole blood, plasma, and isolated blood cells. Rates of degradation of each nucleotide in cell-free plasma ranged from 0.07-0.32 nmol/min/ml with 1 microM substrates to 1.1-3.6 nmol/min/ml with 100 microM substrates. The pattern of catabolism indicated that sequential dephosphorylation from ATP----ADP----AMP----adenosine occurs. In whole blood, the pattern was similar although ATP and ADP (but not AMP) breakdown was more rapid. This was due to leukocyte ectonucleotidase activity. The use of selective inhibitors demonstrated that catabolism was not due to nonspecific phosphatase activity and that plasma 5'-nucleotidase is distinct from ATPase or ADPase. In leukocytes, ATPase and ADPase activities were distinguishable, and each contributed substantially to the rates of catabolism in whole blood. Leukocyte 5'-nucleotidase did not measurably contribute to AMP dephosphorylation in blood. By comparison, ecto-ATPase and ecto-ADPase activities on cultured human umbilical vein endothelial cells were similar to those on leukocytes while endothelial 5'-nucleotidase per 10(6) cells was equivalent to the soluble activity in 1 ml of blood or plasma.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Metabolism of adenine nucleotides in human blood. 254 57

Cultivated endothelial cells of calf aorta (line BKEz-7) possess an effective ectophosphatase system (enzyme activities: ATPase 38.0 +/- 10.2; ADPase 9.2 +/- 4.2; 5'-nucleotidase 4.1 +/- 2.6 fmol/cell.min). Drugs with central depressive activity such as promazine, chlorpromazine, and meprobamate inhibit the activity of the ecto-ATPase. A possible connection between the inhibitory activity on the ecto-ATPase and their central depressive effects is discussed.
...
PMID:[The ectophosphatase activity of cultured endothelial cells of calf aorta and the effect of drugs on ecto-ATPase]. 255 7

1. The synaptosomal fraction isolated from hypothalamus of adult rats on a sucrose density gradient hydrolyzes the labile phosphates from ATP and ADP, thereby satisfying the general definition of apyrase activity. 2. The parallel behavior of ATPase and ADPase activities under different reaction conditions suggests the presence of a "true" apyrase enzyme. The optimum conditions for the reaction are the same for both nucleotides: pH 8.0, 0.6 mM nucleotide and 1.5 mM cation. At temperatures between 10 and 40 degrees C, both activities increase with no change in the ATP/ADP hydrolysis ratio. Thermal inactivation or inhibition of the enzyme activity by iodoacetamide, p-hydroxymercuribenzoate or 2-mercaptoethanol affected the hydrolysis of both substrates in a similar manner. 3. Adenylate kinase and pyrophosphatase activities were not detected in the preparation. 4. The enzyme is located on the outer surface of the synaptosomal membrane: intact and lysed synaptosomes have similar activity and the supernatant obtained by centrifugation of intact synaptosomal preparations does not hydrolyze ATP or ADP.
...
PMID:Synaptosomal apyrase in the hypothalamus of adult rats. 255 77

Mature secretory granules in paraneurons contain ATP amongst other small messenger molecules. In the islet organ such stores of adenine nucleotides readily can be demonstrated by means of the quinacrine fluorescence method. ATP is co-released together with other granule constituents when the major hormones are exocytosed. The distribution of ATP splitting enzymic activities was studied in the pancreas of the mouse and rat, in order to obtain information on the possible fate of this small messenger molecule. ATPase, ADPase, and AMPase (5'-nucleotidase) were demonstrated with lead precipitation methods, L-tetramisole was used to inhibit unspecific alkaline phosphatase (alPase); alPase activities were shown with tetrazolium methods, using 5-bromo-4-chloro-3-indoxyl phosphate as substrate. Most endothelial cells of the vascular bed, both in the exocrine and in the endocrine pancreas, are reactive for ATPase, ADPase, AMPase and alPase. Smooth muscle cells are strongly reactive for ATPase and AMPase, vascular adventitial fibroblasts (veil cells) stain for ATPase and alPase, as do some lamellar cells at the islets surface. Staining for ADPase serves as a selective method to demonstrate the vascular bed. Comparable results are obtained with the alPase reaction, though insular non-B-cells are also reactive. ATPase staining is less useful for demonstrating vascular connections because moderate reactivity of exocrine parenchyma and adventitial tissue obscures the picture. AMPase activity is strong in the venous segments of the capillary net and in collecting veins but the reaction obviously does not demonstrate significant portions of the residual capillary network. Weak AMPase activity is seen in the insular parenchyma.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Fate of ATP in secretory granules: phosphohydrolase studies in pancreatic vascular bed. 255 47


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---