Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The respiration and aerobic glycolysis of pig ciliary processes in oxygenated phosphate and bicarbonate buffers have been investigated. 2. Significant amounts of lactic acid are produced only in the presence of added glucose, but this does not change the endogenous respiration rate. 3. Succinate and citrate increase the oxygen uptake considerably, but pyruvate has almost no effect; oxaloacetate and fumarate stimulate slightly in the presence of glucose. Aspartate and fumarate together stimulate pyruvate utilization and are oxidized as fast as citrate. 4. Ouabain inhibits the oxidation of glucose and other substrates by limiting the ADP supply from the sodium transport system. Cyanide and azide inhibit respiration and stimulate glycolysis. 5. The transport mechanism depends largely on ATP from oxidative phosphorylation and regulates the rate of respiration and glycolysis by controlling ADP production from the Na(+)-K(+)-activated adenosine triphosphatase.
 ...
PMID:The tricarboxylic acid cycle and glycolysis in relation to ion transport by the ciliary body. 591 34

A Mg-dependent adenosine triphosphatase (ATPase) activated by submicromolar free Ca2+ was identified in detergent-dispersed rat liver plasma membranes after fractionation by concanavalin A-Ultrogel chromatography. Further resolution by DE-52 chromatography resulted in the separation of an activator from the enzyme. The activator, although sensitive to trypsin hydrolysis, was distinct from calmodulin for it was degraded by boiling for 2 min, and its action was not sensitive to trifluoperazine; in addition, calmodulin at concentrations ranging from 0.25 ng-25 micrograms/assay had no effect on enzyme activity. Ca2+ activation followed a cooperative mechanism (nH = 1.4), half-maximal activation occurring at 13 +/- 5 nM free Ca2+. ATP, ITP, GTP, CTP, UPT, and ADP displayed similar affinities for the enzyme; K0.5 for ATP was 21+/- 9 microM. However, the highest hydrolysis rate (20 mumol of Pi/mg of protein/10 min) was observed at 0.25 mM ATP. For all the substrates tested kinetic studies indicated that two interacting catalytic sites were involved. Half-maximal activity of the enzyme required less than 12 microM total Mg2+. This low requirement for Mg2+ of the high affinity (Ca2+-Mg2+)ATPase was probably the major kinetic difference between this activity and the nonspecific (Ca2+ or Mg2+)ATPase. In fact, definition of new assay conditions, i.e. a low ATP concentration (0.25 mM) and the absence of added Mg2+, allowed us to reveal the (Ca2+-Mg2+)ATPase activity in native rat liver plasma membranes. This enzyme belongs to the class of plasma membrane (Ca2+-Mg2+)ATPases dependent on submicromolar free Ca2+ probably responsible for extrusion of intracellular Ca2+.
 ...
PMID:A high affinity calcium-stimulated magnesium-dependent ATPase in rat liver plasma membranes. Dependence of an endogenous protein activator distinct from calmodulin. 611 12

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.
 ...
PMID:Nucleotide hydrolysis by solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. 613 88

A procedure for the purification of Mg2+ adenosine triphosphatase (EC 3.6.1.3) from free-living and bacteroid forms of Rhizobium lupini NZP2257 is described. The enzyme was released from cell envelopes using Triton X-100 and purified by gel filtration on Ultrogel AcA 22, followed by preparative gel electrophoresis on agarose. The purified ATPase had a molecular weight of about 355,000, as determined from sedimentation coefficients on sucrose gradients. Kinetic analysis of activity of the enzyme from free-living R. lupini showed it to be typical of F1-type Mg2+ ATPases from bacteria. Mg stimulated activity at pH 7.0, although, when present as the free ion, Mg caused non-competitive inhibition (K1 = 1.5 mM). Maximum activity with ATP occurred over a broad pH range from 6.0 to 10.5. ATP, GTP, and UTP, and, to a much lesser degree, CTP and ADP, were hydrolyzed by the enzyme. Hydrolysis of glucose 6-phosphate was not observed. The Km for ATP at pH 7.0 was 0.67 and for GTP 1.4 mM. ATPase activity was inhibited by ADP, and competitive with ATP (KI = 0.18 mM). Azide also caused inhibition but fluoride and DCCD had no effect. Native and sodium dodecyl sulfate-gel electrophoretic analysis revealed no obvious differences between ATPases from free-living and bacteroid forms of R. lupini.
 ...
PMID:Mg2+ adenosine triphosphatase from cell envelopes of free-living and bacteroid forms of Rhizobium lupini strain NZP2257. 614 93

The platelet content of adenosine triphosphate (ATP), adenosine diphosphate (ADP), serotonin and ouabain-insensitive, magnesium-dependent adenosine triphosphatase (ATPase) was determined in patients with chronic renal failure, patients on chronic hemodialysis, and kidney transplant recipients. Platelet ATP content was normal in all. By contrast, ADP content, expressed in mumol/10(11) platelets, was significantly lower in renal failure: 1.82 +/- 0.96 compared to 2.51 +/- 0.97 in normals (p less than 0.05), but not in dialyzed or transplanted patients; 2.27 +/- 0.96 and 1.87 +/- 0.87, respectively. The mean content of serotonin was also significantly lower in renal failure patients: 0.52 microgram/10(9) platelets as compared to 0.90 microgram/10(9) platelets in normals (p less than 0.05) but was not significantly different in dialyzed and transplanted patients. ATPase was significantly lower in renal failure: 3.13 +/- 1.2 mumol Pi/10(9) platelets in whole suspension and 0.71 +/- 0.22 Pi/mg protein/h in membrane preparation compared to 4.74 +/- 1.1 and 1.18 +/- 0.19, respectively, in normals, and was significantly lower in dialyzed and transplanted patients. Experimental azotemia (BUN 65-86 mg/100 ml), induced by the oral ingestion of urea 2-3 g/kg body weight over 24 h, failed to induce any of these abnormalities. The abnormality in platelet ADP and serotonin content in renal failure paralleled the functional platelet defects which characterize these patients and were reversible following dialysis and transplantation.
 ...
PMID:Biochemical abnormalities of platelets in renal failure. Evidence for decreased platelet serotonin, adenosine diphosphate and Mg-dependent adenosine triphosphatase. 621 10

Binding of nucleotides to the high-affinity site of the isolated alpha subunit of normal Escherichia coli F1 adenosine triphosphatase (ATPase) results in partial protection against digestion by trypsin [Senda, Kanazawa, Tsuchiya & Futai (1983) Arch. Biochem. Biophys. 220, 398-440]. In contrast, the isolated alpha subunit from the defective ATPase of the E. coli uncA401 mutant (strain AN120) is cleaved by trypsin to peptides of less than 8000 Da in the presence of ADP or ATP (2.5 microM-110 mM). The nucleotide-dependent accessibility of thiol groups of the isolated alpha subunit was also studied. Two out of four thiol groups of the alpha subunit from normal ATPase are labelled by fluorescent maleimides or iodoacetates, but in the presence of ADP or ATP (0.14-1.2 mM), reaction of thiol groups with these labels is almost absent. Mutant alpha subunit, however, is labelled by these reagents at all four thiol groups in the presence or absence of ADP or ATP (1 mM). These results suggest that the mutation in the ATPase of strain AN120 leads either to the loss of the high-affinity nucleotide-binding site or affects transmission of allosteric changes that occur on binding of nucleotide to the isolated alpha subunit.
 ...
PMID:Loss of protection by nucleotides against proteolysis and thiol modification in the isolated alpha-subunit from F1 ATPase of Escherichia coli mutant uncA401. 623 16

Previous experiments (Fukushima, Y., and Post, R.L. (1978) J. Biol. Chem. 253, 6853-6862) demonstrated that the Ca x phosphoenzyme of sodium- and potassium-transport adenosine triphosphatase gradually becomes stable after dissociation of Ca2+ in the presence of a chelating agent such as 1,2-cyclohexylenedinitrilo-tetraacetic acid. In the present study, we investigated whether the ADP- and K+-sensitive forms of the Ca x phosphoenzyme show different affinities for divalent cations. Our findings were as follows. (a) As the concentraion of Na+ was increased during phosphorylation of the enzyme with ATP at pH 7.4 and 0 degrees C, both the sensitivity to ADP and the amount of calcium-free phosphoenzyme increased in parallel. (b) For this Na+-dependent change, kidney enzyme required higher concentrations of Na+ than did brain enzyme. (c) In addition, the rate of dissociation of Ca2+ from the ADP-sensitive Ca x phosphoenzyme was faster than that from the K+-sensitive phosphoenzyme. It was thus concluded that Ca2+ binds to the ADP-sensitive phosphoenzyme less tightly than to the K+-sensitive phosphoenzyme.
 ...
PMID:Changes in affinity of Na+- and K+-transport ATPase for divalent cations during its reaction sequence. 624 14

Monensin concentrations between 0.5 and 30 microM produced dose-dependent positive inotropy when administered to normal, electrically driven rabbit left atria. These doses did not produce contracture. When monensin was combined with very low concentrations of ouabain (10 or 50 nM), irreversible contracture, irregular responses to electrical stimulation, or both, occurred in a significant number of atria treated with both drugs. This was apparently due to intracellular Na+ overload produced by both drugs, with secondary elevations of intracellular Ca++ concentrations. Monensin (17 nM, 1.7 or 170 microM) did not inhibit canine myocardial Na+mK+-adenosine triphosphatase activity. When administered to mitochondria isolated from normal rabbit hearts, monensin concentrations greater than 10 nM significantly depressed ADP-stimulated (State 3) respiratory rates and calculated respiratory control ratios. Maximum inhibition of the respiratory control ratio (85% decrease) occurred with monensin concentrations of 1 microM or more. These concentrations also significantly decreased calculated ADP:0 ratios. The data show that monensin concentrations required to increase contractility of isolated myocardium can produce marked inhibitory effects on isolated mitochondria, but apparently do not do so when the drug is administered to intact, normal cardiac tissue.
 ...
PMID:Subcellular actions and potential adverse cardiac effects of the cardiotonic ionophore monensin. 624 11

The rate of phosphorylation of sodium and potassium ion-transport adenosine triphosphatase by 10 microM [gamma-32P]ATP was much slower with Ca2+ than with Mg2+ (0.13-10 mM) in the presence of 16 to 960 mM Na+ at 0 degrees C and pH 7.4. In the presence of a fixed concentration of Mg2+ or Ca2+, the rate became slower with increasing Na+ concentration. When the Na+ concentration was fixed, the rate became slower with decreasing divalent cation concentration. Sodium ions appear to antagonize the divalent cation in the phosphorylation to slow its rate. In the presence of 1 mM Ca2+ and 126 or 270 mM Na+, the rate was slow enough to permit the manual addition of a chasing solution at various times before the phosphorylation reached the steady state. Therefore, we studied the time-dependent change of the sensitivity to ADP or to K+ of the phosphoenzyme by a chase with unlabeled ATP containing ADP or K+ during the time range from the transient to the steady state of the phosphorylation. The ADP sensitivity decreased and the K+ sensitivity increased with the progress of the phosphorylation. With 270 mM Na+, the phosphoenzyme found at 1 s, when its amount was 5.5% of the maximum level, was virtually completely sensitive to ADP. Under these conditions, it was concluded that the form of the phosphoenzyme initially produced from the enzyme.ATP complex has ADP sensitivity and that the phosphoenzyme acquires K+ sensitivity later. The initially produced ADP-sensitive phosphoenzyme partially lost its normal instability and sensitivity upon adding a chelating agent, probably because of dissociation of a divalent cation from the phosphoenzyme.
 ...
PMID:Transient state in the phosphorylation of sodium- and potassium- transport adenosine triphosphatase by adenosine triphosphate. 626 64

Cellular oxygen consumption was monitored during stimulation and inhibition of the Na+- and K+-dependent adenosine triphosphatase in a suspension of intact tubules isolated from the rabbit renal cortex. Respiratory rates were compared to the ADP-stimulated respiratory rate (state 3 rate) obtained in mitochondria released directly from the renal tubules by digitonin shock. At 37 degrees C, in the presence of NADH-linked substrates and fats, isolated renal cells respire at 50 to 60% of the state 3 rate. Inhibition of the (Na+,K+)-ATPase with the cardiac glycoside, ouabain, results in a decline in respiration to 25 to 30% of the state 3 rate. Stimulation of the (Na+,K+)-ATPase produced as a result of nystatin-mediated dissipation of plasma membrane Na+ and K+ gradients results in increased respiration with an oxygen consumption rate characteristic of optimal ATP synthesis (state 3). The relationship between metabolic substrate regimen, mitochondrial respiratory capacity, and cellular energy demand is examined in the context of these findings.
 ...
PMID:Mitochondrial respiratory capacity and Na+- and K+-dependent adenosine triphosphatase-mediated ion transport in the intact renal cell. 627 Jan 7


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