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

To assess the possible role of the Na+ pump in mediating physiological responses to thyroid hormone in the rat myocardium, we examined the effects of L-3,5,3'-triiodothyronine (T3) on the activities of the closely associated enzymes, Na+-K+-dependent adenosine triphosphatase (Na-K-ATPase) and K+-dependent p-nitrophenyl phosphatase (K-dep-pNPPase). In hypothyroid rats, administration of T3 (50 microng/100 g body wt) resulted in significant increases (greater than 50%) in Na-K-ATPase and K-dep-pNPPase activities in both crude homogenates and microsomal fractions of the rat ventricle. Significant effects on Na-K-ATPase activity were also attained with low doses (1 microng/100 g body wt) of T3. A method was developed for assaying K-dep-pNPPase activity in cardiac slices. With this technique, enhancement in K-dep-pNPPase activity of 89.2% was found in ventricle slices after treatment of hypothyroid rats with T3 (50 microng/100 g body wt), implying that augmentation of the capacity of the Na+ pump is achieved in vivo. The potent analogue, L-3,5-diiodo-3' isopropyl thyronine (isopropyl T2) had the same effects on cardiac growth and Na-K-ATPase as T3, in hypothyroid rats. In contrast, the relatively inactive isomer, L-3,3',5'-triiodothyronine (reverse T3) had no significant effect on the heart weight-to-body weight ratio or on ventricular Na-K-ATPase activity.
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PMID:Thyroid hormone control of Na+-K+-ATPase and K+-dependent phosphatase in rat heart. 19 6

Inorganic lead ion in micromolar concentrations inhibits Electrophorus electroplax microsomal (Na+ + K+)-adenosine triphosphatase ((Na+ + K+)-ATPase) and K+-p-nitrophenylphosphatase (NPPase). Under the same conditions, the same concentrations of PbCl2 that inhibit ATPase activity also stimulate the phosphorylation of electroplax microsomes in the absence of added Na+. Enzyme activity is protected from inhibition by increasing concentrations of microsomes, ATP, and other metal ion chelators. The kinetics follow the pattern of a reversible noncompetitive inhibitor. No kinetic evidence is elicited for interactions of Pb2+ with Na+, K+, Mg2+, ATP, or p-nitrophenylphosphate. Na+- ATPase, in the absence of K+, and (Na+ + K+)-NPPase activity at low [K+] are also inhibited. ATP inhibition of NPPase is not reversed by Pb2+. The calculated concentrations of free [Pb2+] that produce 50% inhibition are similar for ATPase and NPPase activities. Pb2+ may act at a single independent binding site to produce both stimulation of the kinase and inhibition of the phosphatase activities.
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PMID:Inhibition by lead ion of Electrophorus electroplax (Na+ + K+)-adenosine triphosphatase and K+-p-nitrophenylphosphatase. 19 41

p-Nitrophenyl phosphatase (p-NPPase) activity of (Na+-K+)-activated adenosine triphosphatase ((Na+-K+)-ATPase) on the acinar cells of dog submandibular gland was demonstrated by using light microscopy. The reaction products of p-NPPase of fresh frozen sections were seen to be localized on the basal parts of acini, and disappeared when the sections were incubated in medium containing 10(-3) Mouabain or in a K-free medium. Under the electron microscope, the reaction products of ATPase were found to be localized on the basolateral plasma membrane of both serous and mucous cells. On the microvilli of the luminal plasma membrane of the acinar cell, a small quantity of the reaction products was also present. This localization of ATPase reaction products on the serous and mucous cells seemed to coincide well with that of p-NPPase activity observed on the acini under light microscopy. Possible explanations are given regarding distribution of the above mentioned enzymes in relation to the cation transport of the plasma membrane. Structural and functional asymmetrical properties of acinar cells of the dog submandibular gland are also discussed.
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PMID:Histochemical and cytochemical localization of (Na+-K+)-activated adenosine triphosphatase in the acini of dog submandibular glands. 21 93

The activity of the electrolyte transport enzyme, sodium, potassium-activated adenosine triphosphatase (Na+,K+-ATPase), in the gills of the pinfish, Lagodon rhomboides, increased markedly following transfer of fish from brackish water to seawater. Cytochemical localization of Na+,K+-ATPase via its potassium-dependent phosphatase (K+-NPPase) activity in the branchial epithelium of pinfish adapted to seawater demonstrated that chloride cells are the major sites for the enzyme. Subcellularly, the heaviest depositions of reaction product were observed lining the cytoplasmic membrane surfaces of the labyrinth of anastomosing plasma membrane tubules that ramifies throughout the chloride cell cytoplasm. Enzyme activity was demonstrated also on the cytoplasmic surface of the apical crypt membrane and on the cytoplasmic surfaces of vesicles in the cytoplasm subjacent to the crypt. Deletion of potassium from the cytochemical incubation medium or inclusion of 10 mM ouabain abolished the reaction products associated with these membranes. The significance of these cytochemical results is discussed with reference to current hypotheses of chloride cell function.
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PMID:Ultracytochemical localization of Na+,K+-activated ATPase in chloride cells from the gills of a euryhaline teleost. 21 85

Whole sheets of plasma membrane, each with their attached flagellum, were purified from Trypanosoma brucei. The method devised for their isolation included a new technique of cell breakage that used a combination of osmotic stress followed by mechanical sheer and avoided the problem of extreme vesiculation as well as the trapping of organelles in cell 'ghosts'. The purified membranes all contained the pellicular microtubular array. The antigenic surface coat was completely released from the plasma membrane during the isolation procedure. The membranes had a very high cholesterol/phospholipid ratio (1.54). A large proportion (42%) of the cellular DNA was recovered in the plasma-membrane fraction unless a step involving deoxyribonuclease treatment, which decreased the DNA content to less than 13%, was included before secrose-density gradient centrifugation. This step also aided the separation of plasma membranes from other cellular components. The ouabain-sensitive Na+ + K+-stimulated adenosine triphosphatase and adenylate cyclase co-purified with the plasma membranes. Although 5'-nucleotidase was thought to be a plasma-membrane component, it was easily detached from the membrane. The purified membranes were essentially free of L-alanine-alpha-oxoglutarate aminotransferase, L-asparte-alpha-oxoglutarate aminotransferase, malate dehydrogenase, oligomycin-sensitive adenosine triphosphatase, glucose 6-phosphatase, Mg2+-stimulated p-nitrophenyl phosphatase and catalase.
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PMID:The isolation and partial characterization of the plasma membrane from Trypanosoma brucei. 48 94

The inhibitory effects of Ca channel antagonists on gastric acid secretion [[14C]-aminopyrine (AP) uptake ratio] have been analyzed in isolated rabbit parletal cells (PC). Secretagogue-stimulated AP uptake was inhibited by verapamil and diltiazem in a dose-dependent manner with IC50 values of 15 and 100 microM, respectively, both in the presence and absence of extracellular Ca. In contrast, nifedipine had no effect on AP accumulation. Verapamil decreased histamine-stimulated respiration with the same IC50 as observed for AP uptake. Imidazole, a weak base, by buffering the acid spaces in PC, reversed the inhibitory effect of verapamil on respiration. In the bullfrog gastric mucosa, forskolin-stimulated proton transport was inhibited by verapamil (10(-4) M) from the luminal but not the serosal side. This inhibitory effect was reversed by either elevating KCl concentration in, or removing the drug from, the secretory solution. Verapamil inhibited gastric microsomal H+,K(+)-adenosine triphosphatase (H+,K(+)-ATPase) and PC K(+)-stimulated p-nitrophenyl phosphatase activities with a higher potency than diltiazem. Inhibition of these enzymes by verapamil and diltiazem was pH dependent. The drugs competed with K+ in both H+,K(+)-ATPase and K(+)-stimulated p-nitrophenyl phosphatase reactions. Our data suggest that inhibition of the gastric proton pump by verapamil or diltiazem is not due to their Ca channel antagonism but to their interaction with the luminal high affinity K(+)-site of the H+,K(+)-ATPase under acidic conditions.
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PMID:Mechanisms of gastric proton pump inhibition by calcium channel antagonists. 215 90

Mercuric chloride (HgCl2), a neurotoxic compound, inhibited the adenosine triphosphatase (ATPase) system in a concentration-dependent manner. Hydrolysis of ATP was linear with time with or without HgCl2 in the reaction mixtures. Higher inhibition of (Na(+)-K+)ATPase activity by HgCl2 was observed in alkaline (8.0 to 9.0) pH and at lower temperatures (17 to 32 degrees). Activation energy values were increased slightly in the presence of HgCl2. Activation of (Na(+)-K+)ATPase by ATP in the presence of HgCl2 showed a decrease in Vmax from 15.29 to 5.0 mumol of inorganic phosphate (Pi)/mg protein/hr with no change in Km. Similarly, activation of K(+)-stimulated p-nitrophenyl phosphatase (K(+)-PNPPase) in the presence of HgCl2 showed a decrease in Vmax from 3.26 to 1.35 mumols of p-nitrophenol (PNP)/mg protein/hr with no change in Km. K(+)-activation kinetic studies indicated that HgCl2 decreased Vmax from 14.01 to 4.30 mumols Pi/mg protein/hr in the case of (Na(+)-K+)ATPase and from 3.45 to 2.40 mumols PNP/mg protein/hr in the case of K(+)-PNPPase with no changes in Km. Na(+)-activation of (Na(+)-K+)ATPase in the presence of HgCl2 showed a decrease in Vmax from 11.06 to 3.23 mumols Pi/mg protein/hr and an increase in Km from 1.06 to 2.08 mM. Preincubation of microsomes with sulfhydryl (SH) agents dithiothreitol, cysteine and glutathione protected HgCl2-inhibition of (Na(+)-K+)ATPase. The data suggest that HgCl2 inhibited (Na(+)-K+)ATPase by interfering with the dephosphorylation of the enzyme-phosphoryl complex.
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PMID:Effect of mercuric chloride on the kinetics of cationic and substrate activation of the rat brain microsomal ATPase system. 216 72

1. Lead, ouabain and an endogenous plasma inhibitor were all found to be potent inhibitors of purified hog cerebral cortex sodium-potassium-activated adenosine triphosphatase and potassium-stimulated p-nitrophenyl-phosphatase. 2. The kinetic characteristics of inhibition of both enzymes by lead and the endogenous plasma inhibitor differed in several respects. For sodium-potassium-activated adenosine triphosphatase, lead and the endogenous plasma inhibitor were non-competitive inhibitors with respect to potassium; lead was competitive with respect to sodium, whereas the endogenous plasma inhibitor had no effect; lead was competitive with respect to magnesium adenosine triphosphate, whereas the endogenous plasma inhibitor was uncompetitive. For potassium-activated p-nitrophenylphosphatase, both lead and the endogenous plasma inhibitor were competitive with respect to potassium; lead showed a mixed type of inhibition with respect to p-nitrophenylphosphate, whereas the endogenous plasma inhibitor was non-competitive. 3. Lead and the endogenous plasma inhibitor exhibited synergistic inhibitory activity on sodium-potassium-activated adenosine triphosphatase. 4. These results suggest that lead could play a contributory role in the pathogenesis of essential hypertension via an additive inhibition of vascular smooth muscle sodium-potassium-activated adenosine triphosphatase.
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PMID:Effects of lead and a low-molecular-weight endogenous plasma inhibitor on the kinetics of sodium-potassium-activated adenosine triphosphatase and potassium-activated p-nitrophenylphosphatase. 216 8

We employed a modification of our previously reported cerium-based cytochemical method for ouabain-sensitive, K-dependent p-nitrophenylphosphatase (Na-K ATPase) activity to detect ouabain-insensitive, K-stimulated p-nitrophenylphosphatase (K-pNPPase) activity in rat gastric glands. Biochemically, the enzyme activity of gastric glands incubated in a medium containing 50 mM Tricine buffer (pH 7.5), 50 mM KCl, 10 mM MgCl2, 2 mM CeCl3, 2 mM p-nitrophenylphosphate (pNPP), 2.5 mM levamisole, 10 mM ouabain, and 0.00015% Triton X-100, was optimal at pH 7.5-8.0 and decreased above pH 8.5. The amount of p-nitrophenol after incubation increased linearly in proportion to the amount of tissue in the medium. The enzyme activity was inhibited by omeprazole, sodium flouride (NaF), N-ethylmaleimide (NEM), and dicyclohexylcarbodiimide (DCCD). Heat-treated specimens had no enzyme activity. The enzyme activity increased with addition of K ions up to the concentration of 50 mM, and became constant above 50 mM. Cytochemically, the parietal cells of the gastric glands reacted positively for ouabain-insensitive K-pNPPase activity. Intense reaction was observed at the microvilli of the luminal surface and the intracellular canaliculi. The tubulovesicular system showed weak enzyme activity. The reaction products were found as fine, granular, electron-dense deposits in the cytoplasm just beneath the plasma membrane. The ouabain-insensitive K-pNPPase activity detected in this study appears, therefore, to be associated with that of H-transporting, K-stimulated adenosine triphosphatase (H-K ATPase).
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PMID:Detection of ouabain-insensitive H(+)-transporting, K(+)-stimulated p-nitrophenylphosphatase activity in rat gastric glands by cerium-based cytochemistry. 217 37

Small cultures of human amniotic cells were preincubated for 24 h. Human prolactin was then added to the medium. After a further short period of incubation the tubes were chilled, the medium removed and the cells rinsed with saline. The tubes then received cold Tris-sucrose and were frozen, to disrupt the cells. After thawing, adenosine triphosphatase (ATPase) and p-nitrophenyl phosphatase (PNPase) were measured. Buffer was added containing either ATP or PNP and the tubes were incubated for 30 min. Inorganic phosphate released from ATP and p-nitrophenol was measured spectrophotometrically. Prolactin stimulated both enzyme activities. The ATPase log dose-response curve was linear between approximately 12.5 and 200 mIU/l. It was inhibited by ouabain. Isobutyl-1-methylxanthine inhibited the ATPase but not the alkaline phosphatase activity. One of these human amniotic cell enzymes may provide the basis for a sensitive bioassay for human prolactin.
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PMID:Enzyme activation of human prolactin: a potential basis for a bioassay. 247 90


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