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 adenosinetriphosphatase (ATPase) (EC 3.6.1.3) activity in Azotobacter vinelandii concentrates in the membranous R3 fraction that is directly associated with Azotobacter electron transport function. Sonically disrupted Azotobacter cells were examined for distribution of ATPase activity and the highest specific activity (and activity units) was consistently found in the particulate R3 membranous fraction which sediments on ultracentrifugation at 144 000 X g for 2 h. When the sonication time interval was increased, the membrane-bound ATPase activity could neither be solubilized nor released into the supernatant fraction. Optimal ATPase activty occurred at pH 8.0; Mg2+ ion when added to the assay was stimulatory. Maximal activity always occurred when the Mg2+:ATP stoichiometry was 1:1 on a molar ratio at the 5 mM concentration level. Sodium and potassium ions had no stimulatory effect. The reaction kinetics were linear for the time intervals studied (0-60 min). The membrane-bound ATPase in the R3 fraction was stimulated 12-fold by treatment wiTH TRypsin, and fractionation studies showed that trypsin treatment did not solubilize ATPase activity off the membranous R3 electron transport fraction. The ATPase was not cold labile and the temperature during the preparation of the R3 fraction had no effect on activity; overnight refrigeration at 4 degrees C, however, resulted in a 25% loss of activity as compared with a 14% loss when the R3 fraction was stored overnight at 25 degrees C. A marked inactivation (although variable, usually about 60%) did occur by overnight freezing (-20 degrees C), and subsequent sonication failed to restore ATPase activity. This indicates that membrane reaggregation (by freezing) was not responsible for ATPase inactivation. The addition of azide, ouabain, 2,4-dinitrophenol, or oligomycin to the assay system resulted in neither inhibition nor stimulation of the ATPase activity. The property of trypsin activation and that ATPase activity is highest in the R3 electron transport fraction suggests that its probable functional role is in coupling of electron transport to oxidative phosphorylation.
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PMID:Characterization studies on the membrane-bound adenosine triphosphatase (ATPase) of Azotobacter vinelandii. 0 Jan 41

An ATPase stimulated by HCO - ions and other oxybases and inhibited by SCN- has been found in main excretory duct of rat submaxillary gland, a tissue, capable of actively secreting HCO - 3 ions. No such ATPase was found in the rabbit duct, which normally does not secrete HCO - 3. The HCO - 3 ATPase was localized in the plasma membrane fraction of the homogenate, as evidenced by the marker 5'-nucleotidase. The activities of the HCO - 3 ATPase increased in metabolic alkalosis and decreased in metabolic acidosis in parallel to secretion of HCO - 3 and K+ ions by the duct epithelium. These findings provide further evidence that the membrane-bound HCO - 3 ATPase is involved in active H+/HCO - 3 transport.
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PMID:H+ transport and membrane-bound HCO - 3 ATPase in salivary duct epithelium. 0 8

An electrochemical potential difference for hydrogen ions ( a protonmotive force) was artifically imposed across the membrane of the anaerobic bacterium Streptococcus lactis. When cells were exposed to the ionophore, valinomycin, the electrical gradient was established by a potassium diffusion potential. A chemical gradient of protons was established by manipulating the transmembrane pH gradient. When the protonmotive force attained a value of 215 mV or greater, net ATP synthesis was catalyzed by the membrane-bound Ca++, Mg++ -stimulated ATPase. This was true whether the protonmotive force was dominated by the membrane potential (negative inside) or the pH gradient (alkaline inside). Under these conditions, ATP synthesis could be blocked by the ATPase inhibitor, dicyclohexylcarbodiimide, or by ionophores which rendered the membrane specifically permeable to protons. These observations provide strong evidence in support of the chemiosmotic hypothesis, which states that the membrane-bound ATPase couples the inward movement of protons to the synthesis of ATP.
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PMID:ATP synthesis driven by a protonmotive force in Streptococcus lactis. 0 50

Net synthesis of adenosine 5'-triphosphate (ATP) in energy-depleted cells of Escherichia coli was observed when an inwardly directed protonmotive force was artificially imposed. In wild-type cells, ATP synthesis occurred whether the protonmotive force was dominated by the membrane potential (negative inside) or the pH gradient (alkaline inside). Formation of ATP did not occur unless the protonmotive force exceeded a value of 200 mV. Under these conditions, no ATP synthesis was found when cells were exposed to an inhibitor of the membrane-bound Ca2+- and Mg2+- stimulated adenosine triphosphatase (EC 3.6.1.3), dicyclohexylcarbodiimide, or to a proton conductor, carbonylcyanide-p-trifluoromethoxyphenyl-hydrazone. Adenosine triphosphatase-negative mutants failed to show ATP synthesis in response to either a membrane potential or a pH gradient. ATP synthesis driven by a protonmotive force was observed in a cytochrome-deficient mutant. These observations are consistent with the chemiosmotic hypothesis of Mitchell (1961, 1966, 1974).
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PMID:Protonmotive force as the source of energy for adenosine 5'-triphosphate synthesis in Escherichia coli. 0 27

Sulphatide (cerebroside sulphate) metabolism of C3H/He mouse kidney was investigated in the course of compensatory renal hypertrophy in association with the change of [Na+,K+]-dependent ATPase, arylsulfatase A and beta-galactosidase activity. A remarkable increase in 35S incorporation into kidney sulphatide was observed 24 hours and especially 7 days after unilateral nephrectomy. In contrast, no significant alteration of 32P incorporation into major phospholipids such as phosphatidylcholine, phosphatidylethanolamine and sphingomyelin was demonstrated in the compensatory hypertrophied mouse kidney. [Na+, K+]-dependent ATPase increased to 126% of control in the remaining kidneys on 7 days after operation. Specific increase in 35S specific activity of kidney sulphatide suggests its possible link with the process of active ion transport through membrane-bound [Na+,K+]-dependent ATPase. Arylsulphatase A activity increased to 151% of control on days, while little change was observed in beta-galactosidase activity. These results suggest a sole concern of a turnover of sulphate moiety of sulphatide molecule in the elevated metabolism.
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PMID:Enhancement of sulphatide metabolism in the hypertrophied kidney of C3H/He mouse with reference to [Na+, K+]-dependent ATPase. 0 13

An ATPase stimulated by HCO-3ions and other oxybases and inhibited by SCN- has been found in main excretory duct of rat submaxillary gland, a tissue, capable of actively secreting HCO-3ions. No such ATPase was found in the rabbit duct, which normally does not secrete HCO-3. The HCO-3ATPase was localized in the plasma membrane fraction of the homogenate, as evidenced by the marker 5'nucleotidase. The activities of the HCO-3ATPase increased in metabolic alkalosis and decreased in metabolic acidosis in parallel to secretion of HCO-3 and K+ ions by the rat salivary duct epithelium. In renal cortex tissue, where HCO-3 is actively reabsorbed respectively H+ is secreted, there was also found a parallel change in the activity of the HCO-3ATPase and the rate of active H+ secretion. These findings provide further evidence that the membrane-bound HCO-3ATPase is involved in active H+/HCO-3 transport. The HCO-3ATPase is not only stimulated by HCO-3 but also by other non transportable oxybases, a finding which indicates H+ rather than HCO-3 being the actively transported component of the buffer system. Small concentrations of K+ ions decrease the Km for HCO-3 and thus yield stimulation of the HCO-3-ATPase. Thport changing in parallel with that of H+/HCO-3 may be taken as indicative for a coupled K+-H+-exchange mechanism to which the HCO-3ATPase is linked.
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PMID:The role of HCO3-stimulated ATPase in buffer transport. 1 63

Binding studies of various nucleotides to the purified coupling factor-latent ATPase from Mycobacterium phlei have been carried out using gel filtration, equilibrium dialysis, and ultrafiltration methods. The purified latent ATPase binds 3 mol of ADP per mol of the enzyme with an apparent dissociation constant of 68 muM. Binding of nucleotides occurred in the decreasing order: ADP, epsilon-ATP, epsilon-ADP, UDP, adenyl-5'-yl imidodiphosphate (AMP-P(NH)P), IDP, and adenosine 5'-(alpha,beta-methylene)diphosphate (AdoP(CH2)P). AMP-P(NH)P inhibits both soluble (Ki = 77 muM) and membrane-bound latent ATPase activity. However, AMP-P(NH)P does not affect oxidative phosphorylation in membrane vesicles of M. phlei. AMP-P(NH)P exhibits one binding site per molecule of the enzyme with a dissociation constant of 71 muM. After trypsin treatment of the enzyme, the binding of ADP decreases 35%, while AMP-P(NH)P binding remains unchanged. Moreover, AMP-P(NH)P binding was not displaced by ADP. Studies with sulfhydryl agents showed that, in contrast to AMP-P(NH)P, binding of at least 1 mol of ADP requires the participation of sulfhydryl groups. The results indicate that AMP-P(NH)P and ADP do not share a common binding site and that the latent ATPase enzyme has separate sites for ATP hydrolysis and ATP synthesis.
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PMID:Binding of nucleotides to purified coupling factor-latent ATPase from Mycobacterium phlei. 1 31

Human skin fibroblasts, grown to confluency in the presence of 32P for random labelling of the phospholipids, showed upon 24 h incubation in the presence of either 8 mM L-serine or 4 mM ethanolamine an increased content of phosphatidylserine (150% of control cells) or phosphatidylethanolamine (116% of control cells), respectively. Concomitantly the phosphatidylcholine correspondingly decreased. Upon cell harvesting and gentle enzyme preparation the base-treated cells demonstrated a significantly higher unstimulated, fluoride- and thyrotropin-stimulated activity of adenylate cyclase. The activities of total ATPase, ouabain-sensitive ATPase, 5'-nucleotidase and gamma-glutamyltransferase remained unaltered. When subjecting enzyme preparations from fibroblasts to ultrasonication the activity of adenylate cyclase decreased progressively with energy applied, whereas the activities of the other enzymes were unaltered ((K+ + Na+)-ATPase, 5'-nucleotidase) or even increased (Mg2+-ATPase, gamma-glutamyltransferase). The results have a bearing upon the regulatory function of the phospholipid microenvironment of membrane-bound enzymes.
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PMID:The influence of changes in the phospholipid pattern of intact fibroblasts on the activities of four membrane-bound enzymes. 1 85

Proton influx was measured after imposition of an electrochemical potential difference for protons (delta muH+) across the cell membrane of the anaerobe, Streptococcus lactis. As delta muH+ was increased, there was an approximately parallel increase in proton entry, until delta muH+ attained 175 to 200 mV. At this point, a new pathway became available for proton entry, allowing an abrupt increase in both the rate and extent of H+ influx. This gated response depended upon the value of delta muH+ itself, and not upon the value of either the membrane potential or the pH gradient. For delta muH+ above 175 to 200 mV, elevated proton entry occurred only in cells having a functional membrane-bound Ca2+-stimulated, Mg2+stimulated adenosine 5'-triphosphatase (EC 3.6.1.3). When present, elevated proton entry coincided with the appearance of net synthesis of adenosine 5'-triphosphate catalyzed by this adenosine 5'-triphosphatase. These observations demonstrate that membrane-bound adenosine 5'-triphosphatase catalyzes an obligatory coupling between the inward movement of protons and synthesis of adenosine 5'-triphosphate.
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PMID:Obligatory coupling between proton entry and the synthesis of adenosine 5'-triphosphate in Streptococcus lactis. 2 Nov 65

HeLa cell plasma membranes have been purified after binding cells to polylysine-coated polyacrylamide beads. Cell attachment to beads and membrane recovery were maximal in a sucrose-acetate buffer, pH 5.0, at 25 degrees C. Measurements of ouabain-sensitive NaK-adenosine triphosphatase, membrane-bound 125I-wheat germ agglutinin, and chemical analyses showed that membranes on beads were of comparable or greater purity than membranes isolated by conventional methods. Because the isolation procedure is rapid (approximately 2.5 h), and produces membranes whose protoplasmic surfaces are fully exposed, it should be a useful supplement to standard isolation techniques.
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PMID:Membrane isolation on polylysine-coated beads. Plasma membrane from HeLa cells. 2 Nov 92


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