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)

This study reports on the distribution of bicarbonate-stimulated ATPase in rat intestinal epithelial cells. Brush-border membranes and basolateral membranes were separated from each other and from mitochondrial and other intracellular membranes by differential and density gradient centrifugation. Bicarbonate-sensitive ATPase activity followed the mitochondrial marker succinic dehydrogenase closely throughout all the centrifugation steps. The low HCO3--ATPase activity in purified brush-border and basolateral plasma membranes could be accounted for quantitatively by the small mitochondrial contamination. Consequently, there are no grounds for postulating that this enzyme has a direct role in H+ or HCO3- transport across the rat small intestine.
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PMID:Distribution of bicarbonate-stimulated ATPase in rat intestinal epithelium. 14 Jan 75

Bicarbonate stimulation of hepatic mitochondrial ATPase activity decreased in rats subjected to intense physical training and reached minimum values at the end of the third week. The stimulatory effect of bicarbonate on mitochondrial heart ATPase remained unaffected under equal conditions. ATPase stimulation by dinitrophenol and sensitivity to oligomycin, both in mitochondria from rat liver or heart, were not affected by physical training. Results suggest that stimulation by dinitrophenol and bicarbonate might be due to effects on separate sites of the enzyme.
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PMID:Bicarbonate stimulation of mitochondrial ATPase. Effect of physical training. 14 Apr 43

Biochemical studies of renal tissue have so far not shown the presence of any active pump mechanism other than Na-K-ATPase. In this review of possible transport mechanisms for the ions Na, K, H, Cl, and HCO3, it is suggested that transport of these ions can be coupled to ATPase by conductance (uniport) processes or by ion gradients by co-transport (symport) or countertransport (antiport) systems. These may be neutral or electrogenic. Accordingly, the function of any region of the tubule will be determined by the porter(s) present in the apical or basal-lateral membrane, and by the Na-K-ATPase located almost exclusively in the basal-lateral membrane. Future research in this area will probably define these porters in vesicles isolated from specific cell types of the kidney.
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PMID:Ion pumps in the renal tubule. 14 38

A study has been made to determine whether renal plasma membranes contain an HCO3 stimulated, ouabain insensitive Mg ATPase. Purified mitochondrial, microsomal and brush border membrane fractions have been isolated from rabbit kidney. The microsomal anion-sensitive ATPase activity appears to be entirely of mitochondrial origin on the basis of the effects of inhibitors of mitochondrial Mg ATPase. The brush border membrane fraction is contaminated with mitochondrial fragments and contains an Mg ATPase activity with low anion-sensitivity. Further purification of this fraction causes parallel decreases in anion-sensitivity of the Mg ATPase activity and in cytochrome c oxidase activity. These results indicate that conclusions previously reached by other investigators for a role of anion-sensitive Mg ATPase in the bicarbonate reabsorption of the proximal tubule may no longer be tenable.
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PMID:Is there a plasma-membrane-located anion-sensitive ATPase? II. Further studies on rabbit kidney. 14 30

The bile salt independent fraction (BSIF) of canalicular bile flow from the isolated rat liver perfused with bicarbonate-free perfusate is 50% of that from the liver perfused with bicarbonate-containing perfusate. HCO3-excretion is nearly eliminated and Na+ and Cl- excretion is reduced 50%. Replacement of HCO3- into perfusate increased bile flow by 0.3 microliter/g.min without changing bile acid excretion rate. 5.5-Dimethyl-2,4-oxazolidinedione (DMO) produced a similar effect. DMO was passively distributed between bile and plasma. The data indicate that a bicarbonate transport mechanism is responsible for production of up to 50% of the BSIF. Another weak acid, N-5[5-(2-methoxyethoxy)-2-pyrimidinyl]sulfamoylbenzene (glymidine), was rapidly excreted into bile and increased bile flow by over 2.0 microliter/g.min. Glymidine is probably excreted by an independent organic anion transport mechanism, and any effect on the bicarbonate transport mechanism is obscured. Canaliculus-enriched hepatocyte membrane fractions contained no HCO3-stimulated ATPase activity. Either this enzyme is unimportant in hepatocyte bicarbonate transport or transport occurs across membranes other than the bile canalicular membrane.
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PMID:Importance of bicarbonate in bile salt independent fraction of bile flow. 15 Jul 96

Differential centrifugation of rat small intestinal homogenates produced a crude brush border (BB) fraction that was enriched 15-fold for the marker enzymes, alkaline phosphatase and sucrase; contamination with mitochondrial enzymes, monoamine oxidase and succinate dehydrogenase, was minimal. ATP hydrolysis by this BB fraction was stimulated by addition of several anions to the incubation medium: HCO3 and Cl were equally effective in this regard, with NO3, NO2, SO4, and acetate being less stimulatory. SCN and CNO inhibited ATPase activity, whereas the divalent anion SO3 was stimulatory at low concentrations (less than 25 mM) but inhibitory at 100 mM. Maximum anion stimulation was observed at a Mg concentration of 0.5 mM, and pH optimum was 8.5. Kinetic analysis showed that HCO3 increased the Vmax without altering the Km for ATP; the Ka for this effect of HCO3 was 35 mM. This enzyme activity was completely inhibited by 20 mM L-phenylalanine, 10 mM L-cysteine, and 3 mM EDTA, compounds that also inhibited intestinal alkaline phosphatase. These results demonstrate the presence of anion-stimulated ATPase activity in rat small intestinal brush border and suggest that this activity may be related to intestinal alkaline phosphatase. The role of this enzyme in intestinal transport is not known, but could relate to the regulation of intestinal absorption and secretion.
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PMID:Anion-stimulated ATPase activity of brush border from rat small intestine. 15 3

The effect of chronic NH4Cl-induced acidosis on the activity of a bicarbonate-activated component of ATPase was studied in homogenates of renal tissue from Wistar rats. This particular component of ATPase, which is maximally stimulated by 50 mM bicarbonate, and is insensitive to the action of ouabain, has been implicated in the active transport of bicarbonate in various tissues. The activity of this enzyme in cortical homogenates from an acidotic group of animals was 4.3 +/- 0.4 mumol Pi/mg protein per hour compared with 5.8 +/- 0.3 mumol Pi/mg protein per hour in a control group (p less than 0.02). No significant change in bicarbonate ATPase activity was observed in medullary homogenates, and NaK-ATPase activity remained the same in cortex and medulla of both groups. Subcellular fractionation of the cortical tissue homogenates revealed that bicarbonate ATPase activity in a microsomal fraction from acidotic animals was 6.5 +/- 1.1 mumol Pi/mg protein per hour compared with 9.4 +/- 1.2 mumol Pi/mg protein per hour in control animals (p less than 0.02). Bicarbonate ATPase activity in other subcellular fractions was not different in the two groups of animals. These findings are compatible with the hypothesis that a certain percentage of bicarbonate reabsorption in the nephron is mediated by a bicarbonate-activated component of ATPase.
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PMID:Bicarbonate-activated ATPase activity in renal cortex of chronically acidotic rats. 15 59

The existence of a membrane-bound HCO3-stimulated ATPase in intestinal mucosa is controversial. A crude brush border fraction of rat small intestinal homogenates contained HCO3-ATPase activity which was inhibited by preincubation with 3 mM EDTA. Alkaline phosphatase activity of this preparation was also inhibited in a parallel, time-dependent fashion by preincubation with EDTA. When 5 mM ZnSO4 accompanied 3 mM EDTA in the preincubation mix, preservation of both enzyme activities occurred, demonstrating a requirement of Zn for the activity of both these phosphatases. These studies support the earlier contention that HCO3-ATPase and alkaline phosphatase activities may be different properties of the same enzyme, and raise the possibility that the ATPase could play a role in intestinal ion transport. The failure to identify a membrane-bound HCO3-ATPase by other workers could be due to the exposure of EDTA which occurred in their tissue preparation.
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PMID:Requirement of Zn to demonstrate HCO3-stimulated ATPase activity of rat small intestinal brush border. 15 7

Two fractions of gastric mucosal membranes obtained by Ficoll-sucrose density gradient centrifugation were studied by a variety of techniques to localize the polypeptides. Gel electrophoresis showed the presence of five major polypeptides and several minor ones. Only one of these, 82,000 daltons, was available for iodination in the intact tissue. The two membrane fractions differed in their accessibility to peroxidase. The denser fraction showed two major defined iodination peaks at 82,000 and 102,000 daltons. Freeze-thawing and iodinating with 131-I produced additional labeling of peaks as well as relabeling the 82,000-dalton component, showing it was accessible from both sides of the membrane. The two major components were also sensitive to cross-linking, the 102,000 polypeptide being especially sensitive to --SH oxidation. Proteolysis with trypsin removed both components in the denser membrane fraction, in addition to inhibiting the K+-ATPase and K+-p-nitrophenylphosphatase of that fraction. Phosphorylation with [gamma-32-P]ATP labeled the 102,000-dalton component and K+, HCO3- minus and p-nitrophenylphosphate reduced the level of labeling. Hence the 102,000 region contains a subunit of the ATPase, is readily iodinated in inside-out vesicles, and is the most available for interpeptide S--S cross-linking.
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PMID:Characterization of gastric mucosal membranes. VIII. The localization of peptides by iodination and phosphorylation. 16 6

Treatment of either beef heart or rat liver mitochondrial ATPase with the arginine reagent, 2,3-butanedione, resulted in enzyme inactivation. The reaction followed pseudo-first order kinetics until 90 to 95% of the enzyme had been inactivated, and prolonged incubation with butanedione resulted in complete inactivation. When the modification reaction was performed in the presence of ATP, the rate of inactivation was significantly decreased. The kinetics of inactivation indicates that the reaction of 1 molecule of reagent per active site of beef heart mitochondrial ATPase is necessary for inactivation. The loss of ATPase activity was also observed when submitochondrial particles were treated with butanedione. Studies with beef heart mitochondrial ATPase indicated that the inactivation was not due to enzyme dissociation into subunits. Kinetic studies with partially inactivated enzyme demonstrated that the Km values of ITP and of ATP in the presence of HCO3-were similar to the same constants for the control enzyme. When ATP was used as the substrate in the absence of anion activator, the partially inactivated enzyme still exhibited negative cooperativity. Inactivation was also observed when beef heart mitochondrial ATPase was treated with another arginine reagent, phenylglyoxal. The loss of ATPase activity was analyzed in terms of [14C]phenylglyoxal incorporation. From the present studies it is concluded that arginyl residues play an essential role in mitochondrial ATPase, probably at the hydrolytic site.
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PMID:Essential arginyl residues in mitochondrial adenosine triphosphatase. 17 62


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