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)

A review of the data on the macromolecular structure of nitrogenase and its individual fragments, the electronic structure of iron- and molybdenum-containing components of the active site, and the functional groups of the ATPase site of the enzyme is given. Reactions of N2 reduction, ATP hydrolysis, and H2 evolution, inhibitory processes, and electron transport reactions catalyzed by the enzyme are analyzed within the framework of a general kinetic model. The results of an investigation of the location of the iron-containing cluster system of electron transport, the ATPase site, and the N2-binding and reducing site on the nitrogenase macro-molecule with the aid of a new complex approach including methods of spin, luminescent, and electron-dense labeling are described. On the basis of a number of physicochemical and kinetic data a model of the structure and mechanism of action of the active site of nitrogenase is proposed, which assumes four-step electron transfer from an external reducing agent along the chain of ferredoxin-like iron-containing clusters of the enzyme and an increase in the reducing potential of the iron clusters through the energy of ATP hydrolysis and four-electron reduction in a binuclear molybdenum-containing complex.
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PMID:Structure and mechanism of catalytic action of active sites of nitrogenase. 15 48

The abundance of mRNA of alpha 1-, alpha 2-, alpha 3-, beta 1-, and beta 2-isoforms of Na(+)-K(+)-ATPase was examined in several renal structures of normal and adrenalectomized (ADX) rats. In situ hybridization with 35S-labeled cRNA probes was performed on kidney sections from adult rats. The number of silver grains per unit surface area was quantified over cells of the glomerulus, proximal convoluted tubules (PCT), early distal tubules (EDT), and cortical collecting ducts (CCD). In normal rat kidney, alpha 1- and beta 1-mRNA was detected in PCT, EDT, and CCD, with the following range of magnitude: EDT > CCD > PCT > glomerulus. The amount of alpha 1- and beta 1-mRNA was equivalent. A large abundance of these two mRNA species was also found in the medullary thick ascending limb of the loop of Henle. Expression of alpha 2, alpha 3, and beta 2 was very low and evenly distributed over any cell type. In ADX, a significant decrease in alpha 1-mRNA (30%) was observed in EDT and CCD, with no change in PCT. beta 1-mRNA abundance was unaffected by adrenalectomy. These results indicate that 1) in the rat kidney alpha 1- and beta 1-mRNA are coexpressed at a similar level that varies along the renal tubule according to the cell type, 2) minute expression of alpha 2-, alpha 3-, and beta 2-mRNA is present in the kidney, and 3) corticosteroid depletion reduces the expression of alpha 1- and not beta 1-mRNA in the corticosteroid-sensitive tubular cells.
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PMID:Adrenalectomy reduces alpha 1 and not beta 1 Na(+)-K(+)-ATPase mRNA expression in rat distal nephron. 132 45

To compare the activity of Na-K-ATPase in the red blood cells (RBCs) and in renal tissue in disorders of Na+ metabolism, the following groups of rats were studied: 1) control, intact rats, 2) adrenalectomized (ADX) rats, 3) intact rats treated with DOCA, 4) ADX DOCA-treated rats, 5) intact salt-loaded rats, 6) ADX salt-loaded rats, 7) intact dexamethasone-treated rats (DEXA), and 8) ADX DEXA-treated rats. After adrenalectomy (group 2) serum Na+ decreased and serum K+ increased. Renal Na-K-ATPase in cortex, medulla and papilla of the control group was 44 +/- 2.7 mumol Pi/mg prot/h, 128.2 +/- 5.9 and 44 +/- 3.2 respectively and in group 2 the enzyme activity was 32.5 +/- 2.0 (P less than 0.005), 81.7 +/- 4.5 (P less than 0.001) and 23.6 +/- 1.9 (P less than 0.001) respectively. RBCs Na-K-ATPase of control animals was 2.82 +/- 0.19 mumol Pi/mg prot/h, while in group 2 the activity was 1.43 +/- 0.24 (P less than 0.001). DOCA treatment of ADX rats (group 4) normalized serum electrolytes and Na-K-ATPase activity in the renal cortex and papilla and in the RBCs. In the renal medulla the correction by DOCA was only partial. Salt loading of ADX rats (group 6) normalized serum electrolytes and Na-K-ATPase activity in the renal medulla and RBCs. Salt loading of normal rats increased RBC Na-K-ATPase to 3.72 +/- 0.36 (P less than 0.02) and medullary Na-K-ATPase to 185.6 +/- 9.8 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Parallel changes in red blood cell and renal Na-K-ATPase activity in adrenal and electrolyte disorders in the rat. 298 67

A cytochemical method was used to measure total, ouabain insensitive and specific (Na-K)ATPase activities along the rat nephron. Enzyme activity was expressed as per cent of mean integrated extinction with reference to a calibrated filter. The lowest mean values of total, ouabain-insensitive, and (Na-K)ATPase activities were found in the proximal convoluted tubule (PCT). In the distal convoluted tubule (DCT), total and ouabain-insensitive activities (77.8 per cent and 45.8 per cent, respectively) were significantly higher than in the medullary thick ascending limb (MAL) (66.0 per cent and 24.6 per cent, respectively). Mean values of (Na-K)ATPase activity were significantly lower in DCT than in MAL (32.0 per cent and 41.3 per cent, respectively). Using Lineweaver-Burk plots, the KM ATP value for total ATPase activity was found to be 2.33, 1.79, and 3.63 mM in DCT, MAL, and PCT respectively. Maximal velocity was lower in PCT than in MAL and DCT. For (Na-K)ATPase, the smallest KM value was found in MAL (0.95 mM) and was 2.73 and 5.71 mM in DCT and PCT respectively. Maximal velocity was the highest in MAL (49.3 per cent), lower in DCT (36.1 per cent) and least in PCT (22.5 per cent). ATPase was measured in the MAL and DCT from rats fed a normal (N-Na+) or a high (Hi-Na+) sodium diet, and from Hi-Na+ rats one week after adrenalectomy (ADX). In the MAL, (Na-K)ATPase tended to be higher in Hi-Na+ than in rats, but was significantly lower in ADX than in Hi-Na+.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:(Na-K)ATPase activity along the nephrons in normal and adrenalectomized rats measured by quantitative cytochemistry. 301 44

Na-K-ATPase activity in the connecting tubule (CNT) and cortical collecting duct (CCD) has been shown to be influenced by KCl both in the presence and in the absence of aldosterone. To investigate if the aldosterone-independent effect of K+ on Na-K-ATPase can be produced by other K+ salts, we studied the effects of dietary KHCO3 on Na-K-ATPase and ouabain-insensitive Mg-ATPase activities in four nephron segments of adrenalectomized (ADX) rabbits. The segments examined were: the distal convoluted tubule (DCT), CNT, CCD and medullary collecting duct (MCD). All diets were similar in composition except their KHCO3 contents which were 100, 300, 500 and 700 meq/kg in groups 1 to 4 respectively. Increasing KHCO3 in the diet increased K+ excretion (7 X) and urine pH (6.6 to 8.3). Na-K-ATPase activity in the CCD increased greater than 200% as dietary KHCO3 was increased to 700 meq/kg. There was a linear relation between Na-K-ATPase activity in this segment and steady state plasma K+ as well as K+ excretion in the urine. However, Na-K-ATPase activity in the CCD was lower in KHCO3-fed ADX rabbits than the KCl-fed animals studied previously under similar conditions. There were no significant differences in Na-K-ATPase activities in DCT, CNT and MCD among the four groups given different KHCO3-diets. It is concluded that dietary intake of KHCO3 can also influence Na-K-ATPase activity in the CCD independent of aldosterone.
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PMID:Effects of potassium bicarbonate on distal nephron Na-K-ATPase in adrenalectomized rabbits. 303 48

Aldosterone-dependent changes in citrate synthase (CS) activity have been used as an index of mineralocorticoid target sites. However, adrenalectomy (ADX) resulted in a fall in activity of CS and several other enzymes in rabbit heart, a tissue with glucocorticoid-but not mineralocorticoid-specific receptors. The enzymes included CS (2.03-1.36 U/mg protein, normal----ADX, P less than 0.001), isocitrate dehydrogenase-NADP+ (1.10-0.80 U/mg, P less than 0.002), isocitrate dehydrogenase-NAD+ (0.034-0.020 U/mg, P less than 0.01), and hydroxymethylglutaryl-CoA lyase (0.072 to 0.035 U/mg, P less than 0.001); in contrast, mitochondrial malate dehydrogenase levels were not significantly reduced by adrenal loss. There was also a decrease after surgery in sarcolemmal Na-K-(17.30-12.31 mumol Pi . mg protein-1 . h-1, P less than 0.002) and Mg-ATPase activities (14.16-12.11 mumol Pi . mg protein-1 . h-1, P less than 0.05). However, ADX did not result in a significant change in heart weight per kilogram body weight or recovery of mitochondrial protein per gram heart. CS was also assayed in hearts from ADX animals following acute (90 min) and chronic (3 day) steroid replacement. Although neither acute intravenous aldosterone (10 micrograms/kg) nor dexamethasone (100 micrograms/kg) increased activity, exposure to multiple subcutaneous injections of either steroid over a 3-day period significantly elevated CS above ADX values. The coordinate changes in the levels of several myocardial enzymes associated with energy metabolism is discussed in terms of an adaptation to chronic alterations in energy demands as opposed to specific mineralocorticoid or glucocorticoid receptor-mediated processes.
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PMID:Influence of adrenalectomy and steroid replacement on heart citrate synthase levels. 614 77

The respective effects of aldosterone and arginine vasopressin (AVP) were examined on the number of active Na(+)-K(+)-ATPase and their pumping activity in nonperfused microdissected mouse cortical collecting tubules (CCD) by measuring specific 3H-ouabain binding and ouabain-sensitive 86Rb uptake. In adrenalectomized (ADX) animals, incubation of CCD with AVP (10(-8) M for 5 min) had no effect on the number of pumps. In contrast, in ADX animals replete with aldosterone, AVP induced a approximately equal to 40% increase in the number of pumps. This was accompanied by a approximately equal to 60-65% increase in ouabain-sensitive Rb uptake. AVP effect was dose-dependent (10(-10)-10(-8) M) and was reproduced by dDAVP, forskolin and 8-Br cAMP, indicating a V2 pathway. It was inhibited by amiloride 10(-5) M, and did not occur in CCD incubated in hyperosmotic solution, suggesting that the signal was transmitted via apical sodium entry and cell swelling. Finally, the AVP-dependent increase in the number of pumps was rapid (within 5 min) and transient (< 25 min). These results demonstrate that, in the CCD, aldosterone and AVP act synergistically to increase not only the apical sodium entry but also the basolateral Na(+)-K(+)-ATPase transport capacity: AVP allows a rapid recruitment and/or activation of an aldosterone-dependent pool of latent Na(+)-K(+)-ATPase.
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PMID:Synergistic action of vasopressin and aldosterone on basolateral Na(+)-K(+)-ATPase in the cortical collecting duct. 763 89

The activities of three mitochondrial oxidative enzymes (citrate synthase, 3-ketoacid-CoA transferase, beta-hydroxyacyl-CoA dehydrogenase) and Na-K-ATPase were microassayed in isolated segments of the rat proximal convoluted tubule (PCT) and medullary thick ascending limb of the loop of Henle (mTAL). The effects of adrenalectomy (ADX) and ADX plus exogenous glucocorticoids were analyzed. The hormonal replacement was daily injections of dexamethasone (10 micrograms/100 g body weight/24 h) for 5 days. ADX lowered the activity of all oxidative enzymes studies in the mTAL, but not in the PCT and led to a decrease in Na-K-ATPase in both nephron segments. Dexamethasone restored the normal level of oxidative enzymes and Na-K-ATPase in the mTAL and of Na-K-ATPase in the PCT. We conclude that the activities of citrate synthase, 3-ketoacid-CoA transferase and beta-hydroxyacyl-CoA dehydrogenase and of Na-K-ATPase are coordinately regulated in the mTAL and that glucocorticoids are essential for the long-term regulation of these enzyme activities in this nephron segment. In contrast, the activities of mitochondrial oxidative enzymes are not influenced by glucocorticoids in the PCT. This study presents the first evidence for a cell-specific regulation by glucocorticoids of oxidative metabolism in the nephron of adult rat kidney.
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PMID:Effect of glucocorticoids on mitochondrial oxidative enzyme and Na-K-ATPase activities in the rat proximal tubule and thick ascending limb of Henle. 769 38

The Na+,K(+)-ATPase plays a key role in the regulation of ion fluxes and membrane repolarization in the CNS. We have studied glucocorticoid effects on biosynthesis of the Na+,K(+)-ATPase and on ouabain binding in the ventral horn of the spinal cord using intact rats, adrenalectomized (ADX) rats, and ADX rats receiving dexamethasone (ADX+DEX) during 4 days. Cryostat sections from spinal cords were incubated with a 35S-oligonucleotide coding for the alpha 3-subunit or a 3H-cDNA coding for the beta 1-subunit of the Na+,K(+)-ATPase using in situ hybridization techniques. In ventral horn motoneurons, grain density per cell and grain density per area of soma for both probes were slightly reduced in ADX rats but significantly increased in the ADX+DEX group, using ANOVA and the Bonferroni's test. Statistical analysis of frequency histograms of neuronal densities further indicated a significant shift to the right for intact rats compared with ADX rats for both probes. Concomitantly, [3H]ouabain binding to membrane preparations from ventral horns was reduced in ADX rats and restored to normal by DEX administration. No effect of adrenalectomy or DEX treatment was obtained in the dorsal horn. In conclusion, glucocorticoids positively modulate the mRNA for the alpha 3-subunit and the beta 1-subunit of the Na+,K(+)-ATPase and recover ouabain binding to normal values. The increments of the synthesis and activity of an enzyme affecting membrane repolarization and synaptic neurotransmission are consistent with the alleged stimulatory effect of glucocorticoids on spinal cord function.
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PMID:Dexamethasone increases adrenalectomy-depressed Na+,K(+)-ATPase mRNA and ouabain binding in spinal cord ventral horn. 793 53

Mitochondrial import stimulation factor (MSF) unfolds wheat germ lysate synthesized aggregated mitochondrial precursor proteins and stimulates their mitochondrial import in an ATP dependent manner. Here we analysed the function of MSF mainly by utilizing chemically pure adrenodoxin precursor (pAd). MSF bound to the unfolded pAd and prevented it from losing import competence and also restored the import competence of the aggregated pAd dependent on ATP hydrolysis. The import incompetent aggregated mitochondrial precursors induced the ATPase activity of MSF and the activity was strongly inhibited by isolated mitochondrial outer membrane (OM) but not by trypsin treated outer membrane (tOM). The precursor induced ATPase activity of N-ethylmaleimide (NEM)-treated MSF was not inhibited by OM. In this context, the MSF-precursor complex specifically bound to OM and binding was abolished both by the treatment of OM with trypsin and by the treatment of MSF with NEM. These results show that MSF is a novel cytoplasmic chaperone protein with a mitochondrial precursor-targeting function.
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PMID:MSF, a novel cytoplasmic chaperone which functions in precursor targeting to mitochondria. 795 79


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