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)

Both nickel-specific transport and nickel transport by a magnesium transporter have been described previously for a variety of nickel-utilizing bacteria. The derepression of hydrogenase activity in Bradyzhizobium japonicum JH and in a gene-directed mutant of strain JH (in an intracellular Ni metabolism locus), strain JHK7, was inhibited by MgSO4. For both strains, Ni2+ uptake was also markedly inhibited by Mg2+, and the Mg(2+)-mediated inhibition could be overcome by high levels of Ni2+ provided in the assay buffer. The results indicate that both B. japonicum strains transport Ni2+ via a high-affinity magnesium transport system. Dixon plots (1/V versus inhibitor) showed that the divalent cations Co2+, Mn2+, and Zn2+, like Mg2+, were competitive inhibitors of Ni2+ uptake. The KiS for nickel uptake inhibition by Mg2+, Co2+, Mn2+, and Zn2+ were 48, 22, 12, and 8 microM, respectively. Cu2+ strongly inhibited Ni2+ uptake, and molybdate inhibited it slightly. Respiratory inhibitors cyanide and azide, the uncoupler carbonyl cyanide m-chlorophenylhydrazone, the ATPase inhibitor N,N'-dicyclohexylcarbodiimide, and ionophores nigericin and valinomycin significantly inhibited short-term (5 min) Ni2+ uptake, showing that Ni2+ uptake in strain JH is energy dependent. Most of these conclusions are quite different from those reported previously for a different B. japonicum strain belonging to a different serogroup.
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PMID:Competitive inhibition of an energy-dependent nickel transport system by divalent cations in Bradyrhizobium japonicum JH. 178 26

The purified Ca2+/Mg2+ ATPase from rat heart plasma membrane was activated by Ca2+ and Mg2+ with Ka values of 1.47 mM and 2.51 mM, respectively; other divalent cations also activated the enzyme but to a lesser extent. Divalent cations like Cu2+, Zn2+, Ni2+, Cd2+ were potent inhibitors of the enzyme activity in the presence of Ca2+ or Mg2+ whereas Na+, K+ or HCO3- did not affect the Ca2+/Mg2+ ATPase activity; the pH optima was 8.5. The enzyme hydrolyzed ATP with a Km of 0.34 mM for Ca2+ ATPase and 0.48 mM for Mg2+ ATPase; various nucleoside triphosphate such as ITP, CTP, GTP, and UTP were also hydrolyzed. Phospholipase A and C as well as neuraminidase decreased the Ca2+/Mg2+ ATPase activity whereas phospholipase D was ineffective. The purified Ca2+/Mg2+ ATPase was found to bind ATP-r-35S with two affinities; the KD values were 50.9 +/- 0.8 and 1160 +/- 198 nM and the Bmax values were 8.71 +/- 0.16 and 145 +/- 9.7 nmol/mg protein for high and low affinity sites, respectively. Treatment of the enzyme preparation with phospholipases and neuraminidase did not affect the ATP-r-35S binding. Ca2+ was also found to bind with Ca2+/Mg2+ ATPase with a KD of 0.384 mM and a Bmax of 1.85 mumol/mg protein; Ni2+, Mn2+, Zn2+ at 1 mM concentrations inhibited the Ca2+ binding but Mg2+ and verapamil were without effect. Phospholipase A and neuraminidase decreased the Ca2+ binding by 20-30%; this indicated that Ca2+ binding with the purified enzyme may be partly due to the phospholipids and sialic acid residues associated with the enzyme. These results show that the purified Ca2+/Mg2+ ATPase is a Ca2+ binding glycoprotein having two binding sites for ATP. Furthermore, this study suggests that phospholipids associated with purified Ca2+/Mg2+ ATPase are required for maximal activity.
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PMID:Characterization of the purified rat heart plasma membrane Ca2+/Mg2+ ATPase. 183 90

Different histochemical identification methods for muscle fibre types have been introduced over the years. Most of them have been based on myosin ATPase activity after different kinds of preincubations, alone or in combination with oxidative enzymes. Comparative studies have shown, however, that the different methods result in nonidentical subgroups of type II fibres. Optical density values of individual fibres after incubation of serial sections for alkali- or copper-preincubated ATPase, NADH-TR, and fibre diameter, combined in two-dimensional plots, have for a long time been used in our laboratory to separate three subgroups of type II fibres. A cluster analysis, based on the data mentioned above, results in three subgroups of type II fibres in rat plantaris muscle. In comparison, earlier studies comparing different histochemical methods and reporting lack of correspondence between them have been based on two subgroups of type II fibres only. It is suggested that part of the lack of correspondence is due to unequal and incomplete separation by the methods used in the comparative studies, and that the three subgroups of type II fibres identified in the cluster analysis are type IIA, IIX and IIB, respectively. The need for a consensus on a common basis for histochemical identification of muscle fibre types is emphasized.
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PMID:How unequivocal is the muscle fibre type concept? 183 5

We have studied the mechanism by which liver Golgi apparatus maintains the acidity of its contents, using a subcellular fraction from rat liver highly enriched in Golgi marker enzymes. Proton accumulation (measured by quenching of acridine-orange fluorescence) and anion-dependent ATPase were characterized and compared. Maximal ATPase and proton accumulation required ATP; GTP and other nucleotides gave 10% to 30% of maximal activity. Among anions, Cl- and Br- approximately doubled the activities; others were much less effective. Half-maximal increase of ATPase and H+ uptake required 55 mmol/L and 27 mmol/L Cl-, respectively. In predominantly chloride media, SCN- and NO3- markedly inhibited H+ uptake. Nitrate competitively inhibited both the chloride-dependent ATPase (apparent Ki 6 mmol/L) and proton uptake (apparent Ki 2 mmol/L). Nitrate and SCN- also inhibited uptake of 36Cl. Replacing K+ with Na+ had no effect on the initial rate of proton uptake but somewhat reduced the steady state attained. Replacement of K+ with NH4+ and choline reduced proton uptake without affecting ATPase. The ATPase and H+ uptake were supported equally well by Mg2+ or Mn2+. The ATPase was competitively inhibited by 4-acetamido-4'-isothiocyano-stilbene-2,2'-disulfonic acid (apparent Ki 39 mumol/L). Other agents inhibiting both H+ uptake and ATPase were N-ethylmaleimide, N,N'-dicyclohexylcarbodiimide, chlorpromazine, diethylstilbestrol, Zn2+, Co2+ and Cu2+. In the Cl- medium, accumulated protons were released by ionophores at the relative rates, monensin = nigericin greater than valinomycin greater than carbonyl cyanide mchlorophenylhydrazone; the last of these also reduced ATPase activity. In the absence of Cl-, monensin and valinomycin both stimulated the ATPase. These results show a close association between ATPase activity and acidification of liver Golgi vesicles. They support a role for Cl- that depends on its uptake as a counter ion for H+ and suggest that it may also stimulate proton transport by a more direct effect on a component of the transport system.
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PMID:Proton accumulation and ATPase activity in Golgi apparatus-enriched vesicles from rat liver. 184 95

Heavy metal ions have been shown to induce Ca2+ release from skeletal sarcoplasmic reticulum (SR) by binding to free sulfhydryl groups on a Ca2+ channel protein and are now examined in cardiac SR. Ag+ and Hg2+ (at 10-25 microM) induced Ca2+ release from isolated canine cardiac SR vesicles whereas Ni2+, Cd2+, and Cu2+ had no effect at up to 200 microM. Ag(+)-induced Ca2+ release was measured in the presence of modulators of SR Ca2+ release was compared to Ca2(+)-induced Ca2+ release and was found to have the following characteristics. (i) Ag(+)-induced Ca2+ release was dependent on free [Mg2+], such that rates of efflux from actively loaded SR vesicles increased by 40% in 0.2 to 1.0 mM Mg2+ and decreased by 50% from 1.0 to 10.0 mM Mg2+. (ii) Ruthenium red (2-20 microM) and tetracaine (0.2-1.0 mM), known inhibitors of SR Ca2+ release, inhibited Ag(+)-induced Ca2+ release. (iii) Adenine nucleotides such as cAMP (0.25-2.0 mM) enhanced Ca2(+)-induced Ca2+ release, and stimulated Ag(+)-induced Ca2+ release. (iv) Low Ag+ to SR protein ratios (5-50 nmol Ag+/mg protein) stimulated Ca2(+)-dependent ATPase activity in Triton X-100-uncoupled SR vesicles. (v) At higher ratios of Ag+ to SR proteins (50-250 nmol Ag+/mg protein), the rate of Ca2+ efflux declined and Ca2(+)-dependent ATPase activity decreased gradually, up to a maximum of 50% inhibition. (vi) Ag+ stimulated Ca2+ efflux from passively loaded SR vesicles (i.e., in the absence of ATP and functional Ca2+ pumps), indicating a site of action distinct from the SR Ca2+ pump. Thus, at low Ag+ to SR protein ratios, Ag+ is very selective for the Ca2+ release channel. At higher ratios, this selectivity declines as Ag+ also inhibits the activity of Ca2+,Mg2(+)-ATPase pumps. Ag+ most likely binds to one or more sulfhydryl sites "on" or "adjacent" to the physiological Ca2+ release channel in cardiac SR to induce Ca2+ release.
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PMID:The heavy metal ions Ag+ and Hg2+ trigger calcium release from cardiac sarcoplasmic reticulum. 213 85

The uncoupler-induced inactivation of H(+)-ATPase in liver mitochondria from ground squirrel has been studied. The dependence of this process on delta mu H+, pH and ATP indicates that it is caused by the protein inhibitor. This conclusion is also supported by the protective effect of Zn2+ and Cu2+. The inactivation can be induced by Ca2+ at low concentrations in the presence of phosphate. It is shown that the protein inhibitor inactivates ATPase almost completely under optimal conditions while its effect in mice or rat liver mitochondria does not exceed 30%. The potential efficiency of the inhibitor's action does not depend on either the season or the state of animals (hibernating or active). At the same time, the sensitivity of this system to Ca2+ is significantly lower in active (summer) animals.
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PMID:Regulation of ATP hydrolysis in liver mitochondria from ground squirrel. 214 5

Vacuolar H(+)-ATPase was isolated from highly purified bovine kidney brush border, using a previously described immunoaffinity method. The affinity purified enzyme had reconstitutively active ATP-induced acidification that was inhibited by N-ethylmaleimide. The brush border H(+)-ATPase had a single pH optimum of 7.3, and a single Km for ATP of 360 microM. The enzyme showed no lipid activation; it had a substrate preference of ATP greater than ITP greater than UTP greater than GTP much greater than CTP, with an ATP:GTP selectivity of 1.69. The brush border H(+)-ATPase required no monovalent anion or cation for activity and was inhibited by the oxyanions NO3(-1) much greater than SO4(-2); sulfite stimulated activity at low concentrations and inhibited at higher concentrations. The inhibition produced by nitrate could not be attributed to dissociation of subunits from the enzyme. The divalent or trivalent cation preference was Mn+2 much greater than Mg+2 much greater than Co+2 greater than Al+3 greater than Ca+2 much greater than Ba+2,Sr+2; 1 mM Zn+2 inhibited the enzyme completely, but Cu+2 inhibited only 49% of activity at concentrations up to 5 mM. Sodium dodecyl sulfate-polyacrylamide gels of the brush border H(+)-ATPase showed subunits at Mr 70,000, a doublet at 56,000, 45,000, 42,000, 38,000, 33,000, 31,000, 15,000, 14,000, and 12,000. On two-dimensional gels, the pl value for the Mr 70,000 subunit was 6.3, for the Mr 56,000 was 6.4, and for the Mr 31,000 was 7.5-8.5, and microheterogeneity was observed in the Mr 56,000 and 31,000 subunits. A comparison of kidney cortex brush border H(+)-ATPase with kidney cortex microsomal H(+)-ATPase revealed differences in pH optimum, Km for ATP, lipid dependence, substrate preference, divalent ion preference, copper sensitivity, and in microheterogeneity of the Mr 56,000 and 31,000 subunits, providing evidence that different functional and structural classes of vacuolar H(+)-ATPase are segregated to specific membrane compartments.
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PMID:Isolation and properties of bovine kidney brush border vacuolar H(+)-ATPase. A proton pump with enzymatic and structural differences from kidney microsomal H(+)-ATPase. 214 91

A (H+ + K+)-ATPase-enriched membrane fraction derived from the fundic portion of hog gastric mucosa was obtained by a combination of differential and repeated 7% Ficoll gradient centrifugation. The microsomal membrane fraction isolated by repeated 7% Ficoll gradient centrifugation was free of ouabain-sensitive (Na+ + K+)-ATPase, 5'-nucleotidase and succinate dehydrogenase; and it was highly enriched in (H+ + K+)-ATPase and K(+)-stimulated p-nitrophenylphosphatase (p-NPPase). The (H+ + K+)-ATPase had a pH optimum of 7.4 and was stimulated by Tl+, K+, Rb+ and NH4+ with Ka values of 0.0667, 0.526, 0.667 and 3.03 mM, respectively, at this pH. On the other hand, monovalent cations such as Na+, Li+ and (CH3)4N+ as well as divalent cations such as Cu2+, Ca2+, Ba2+, Sr2+ and Cd2+ inhibited this enzyme activity concentration-dependently. Ouabain and oligomycin had no effect, whereas omeprazole, a specific (H+ + K+)-ATPase inhibitor, inhibited this enzyme activity in a pH-dependent manner. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis showed a major band (greater than or equal to 90% of protein) at 97,400 daltons, which was phosphorylated in the presence of Mg2+ and [gamma-32P]-ATP and dephosphorylated in the presence of K+. The present method was very simple, and the (H+ + K+)-ATPase activity of the microsomal fraction obtained by this method was much higher compared with those obtained by other methods such as free-flow electrophoresis.
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PMID:Purification and characterization of (H+ + K+)-ATPase from hog gastric mucosa. 215 97

The cellular mechanisms by which nephrotoxic heavy metals injure the proximal tubule are incompletely defined. We used extracellular electrodes to measure the early effects of heavy metals and other sulfhydryl reagents on net K+ and Ca2+ transport and respiration (QO2) of proximal tubule suspensions. Hg2+, Cu2+, and Au3+ (10(-4)M) each caused a rapid net K+ efflux and a delayed inhibition of QO2. The Hg2(+)-induced net K+ release represented passive K+ transport and was not inhibited by barium, tetraethylammonium, or furosemide. Both Hg2+ and Ag+ promoted a net Ca2+ uptake that was nearly coincident with the onset of the net K+ efflux. A delayed inhibition of ouabain-sensitive QO2 and nystatin-stimulated QO2, indicative of Na+, K(+)-ATPase inhibition, was observed after 30 sec of exposure to Hg2+. More prolonged treatment (2 min) of the tubules with Hg2+ resulted in a 40% reduction in the CCCP-uncoupled QO2, indicating delayed injury to the mitochondria. The net K+ efflux was mimicked by the sulfhydryl reagents pCMBS and N-ethylmale-imide (10(-4) M) and prevented by dithiothreitol (DTT) or reduced glutathione (GSH) (10(-4) M). In addition, both DTT and GSH immediately reversed the Ag(+)-induced net Ca2+ uptake. Thus, sulfhydryl-reactive heavy metals cause rapid, dramatic changes in the membrane ionic permeability of the proximal tubule before disrupting Na+, K(+)-ATPase activity or mitochondrial function. These alterations appear to be the result of an interaction of the metal ions with sulfhydryl groups of cell membrane proteins responsible for the modulation of cation permeability.
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PMID:Sulfhydryl-reactive heavy metals increase cell membrane K+ and Ca2+ transport in renal proximal tubule. 230 68

Hog gastric vesicles showed Cl- conductance when treated with Cu2+-o-phenanthroline, an S-S cross-linking reagent. An IgG monoclonal antibody caused dose-dependent inhibition of Cl- conductance that had been induced by S-S cross-linking. The antibody did not cause intervesicular aggregation, as determined by measurement of vesicle size. These results show that Cl- conductance, the stimulation and inhibition of which are regulated reversibly by S-S----2SH transformation, is due to native, physiological channels. The antibody also dose dependently inhibited the activities of H,K-ATPase and p-nitrophenyl phosphatase in gastric vesicles, but did not inhibit Na,K-ATPase obtained from dog kidney. Immunoblotting with the antibody of vesicle proteins solubilized in sodium dodecyl sulfate-polyacrylamide gel showed that the antibody binds to a 95-kDa subunit of H,K-ATPase and its dimeric 180-kDa polypeptide. The antibody-binding sites of H,K-ATPase activity and the Cl- channel for the inhibition were present on the external (cytosolic) surface of the transmembraneous ATPase. A gastric antisecretory compound, 2-methyl-8-(phenylmethoxy)imidazo[1,2 alpha] pyridine-3-acetonitrile (SCH 28080), competitively bound to the high affinity site of K+ on the internal (luminal) surface of H,K-ATPase, and its half-maximal inhibitory concentration for H,K-ATPase activity in tight vesicles was 0.2 microM in the presence of valinomycin. SCH 28080 also dose dependently inhibited opening of Cl- channels by S-S cross-linking, the regulatory site being present on the cytosolic side and more internally than the antibody binding site. The half-inhibitory concentration of SCH 28080 was 0.3 microM. The present results with the antibody and SCH 28080 indicate that the Cl- channel is part of the function of H,K-ATPase.
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PMID:The Cl- channel in hog gastric vesicles is part of the function of H,K-ATPase. 244 90


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