Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.3.1 (Mg2+-ATPase)
 1,484 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

When myofibrils from rat hearts were dissolved in concentrated salt solutions and reprecipitated by dilution, they contained both protein kinase (partly cyclic 3':5'-AMP-dependent) and protein phosphatase activities. Troponin-I was the major protein to be phosphorylated by the endogenous myofibril-associated kinase and by added protein kinase. Approximately 1 mole of phosphate per mole of troponin-I was incorporated from radioactive ATP, but the extent of troponin-I phosphorylation could be varied experimentally. An inverse correlation was found between protein phosphorylation and the maximum Ca2+-stimulated myofibrillar Mg2+-ATPase activity, while the amout of calcium required for half-maximum activation was proportional to the extent of protein phosphorylation. The changes in Mg2+-ATPase activity produced in vitro by protein phosphorylation were reproduced in isolated perfused rat hearts treated for short periods with L-noradrenaline (10(-6)M). The changes in myofibrillar function brought about as the result of the phosphorlyation by cAMP-dependent protein kinase suggest that the contractile response is desensitized in order to cope with the rise in intracellular Ca2+ which results from the action of catecholamines on cardiac ventricular cells.
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PMID:Cardiac myofibrillar phosphorylation and adenosine triphosphatase activity. 22 75

Cortical slices from brains of ethanol-tolerant rats have previously been shown to release a greater fraction of uptake [3H]-noradrenaline ([3H]-NA) on K+-depolarisation than slices from control animals. In the present experiments, when stimulated with the Ca2+ ionophore A23187 (30 microM), untreated cortical synaptosomes release only a very small fraction of uptaken [3H]-NA. Under these conditions synaptosomal preparations from ethanol-tolerant animals released a greater fraction of uptaken [3H]-NA but the difference was not significant. However, after incubation with ouabain (100 microM, to increase intrasynaptosomal [Ca2+]) A23187 now produced a much greater enhancement of [3H]-NA release in preparations from ethanol-tolerant rats. Further, after superfusion of the synaptosomal preparation with 1mM EGTA and A23187 for 30 min (a procedure which should reduce intrasynaptosomal [Ca2+]) the reintroduction of Ca2+ to the superfusing fluid caused a marked release of [3H]-NA which was also significantly greater in preparations from ethanol-tolerant animals. Ca2+/Mg2+-ATPase activity was also higher in these synaptosomes but no difference could be detected in the release of [3H]-NA from a combined synaptic vesicle: synaptic plasma membrane preparation. The results suggest that the development of ethanol tolerance is associated with a fundamental change in the dynamic control of Ca2+ concentrations within the nerve terminal which potentiates the depolarisation-induced release of neurotransmitters.
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PMID:Enhanced [3H]-noradrenaline release in synaptosomes from ethanol-tolerant animals: the role of nerve terminal calcium ion concentrations. 240 91

We have previously presented evidence for the existence of a brain soluble factor which mediates the stimulation of synaptosomal ATPases by catecholamines. The stimulation of synaptosomal ATPases by dopamine plus brain soluble fraction was not modified if the soluble fraction was heated for 5 min at 95 degrees C. One day after preparation, the soluble factor inhibited the Na+, K+-ATPase, but not the Mg2+-ATPase activity, and subsequent addition of noradrenaline stimulated the ATPases activities. The inhibitory effect of a 24 h soluble fraction disappeared if the soluble fraction was dialyzed; in this case, noradrenaline did not activate the enzyme activities. Gel filtration in Sephadex G-50 permitted separating a subfraction which inhibited ATPase activity (peak II) from another which stimulated ATPase activity (peak I). Peak I stimulated both Na+, K+, and Mg2+ ATPases. Peak II inhibited only Na+, K+-ATPase, and when stored acidified, it mediated ATPases stimulation by noradrenaline.
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PMID:Partial characterization of an endogenous factor which modulates the effect of catecholamines on synaptosomal Na+, K+-ATPase. 301 5

Using slices of mouse or rat cerebral cortex incubated with [3H]adenosine or [3H]adenine and/or [14C]GABA we have examined factors affecting the release of these compounds, and especially the influence of methylxanthines. Although release of purines and GABA could be induced by ouabain (10(-4) M), or p-hydroxymercuribenzoate (5 x 10(-4) M) no release was produced by ethacrynic acid (10(-3) or 10(-4) M) phenytoin (10(-3) M), noradrenaline or SC 13504. Release is probably not therefore related to (Na+, K+) ATPase or Mg2+-ATPase inhibition. At concentrations of 10(-3) and 10(-4) M, caffeine, theophylline, aminophylline and isobutyl-methylxanthine (IBMX) markedly depressed the release of purines evoked by ouabain. Non-xanthine inhibition of phosphodiesterase had much weaker though statistically significant effects. The methylxanthines had no significant effect on GABA release. It is suggested that the results can be explained on the basis of a positive feedback system in which released adenosine activates membranal adenylate cyclase, and the increased concentration of cyclic AMP which results form or origin of much of the adenosine released subsequently. However, we cannot exclude the existence of an intracellular receptor for methylxanthines which causes directly the inhibition of purine release.
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PMID:Methylxanthines modulate adenosine release from slices of cerebral cortex. 616 26

Noradrenaline (NA) and isopropyladrenaline in a dose of 11 microM/kg were shown to activate in vivo Na+, K+-ATPase and Mg2+-ATPase in the mouse renal microsomal fraction. NA (10(-6) M) increased the activity of Na+, K+-ATPase in vitro and did not affect the activity of Mg2+-ATPase in the hepatic and renal microsomal fractions. NA did not significantly affect in vivo the mitochondrial ATPases activity in the presence of various stimulators (Mg, dinitrophenol, bicarbonate) and inhibitors (oligomycin, bicyclohexyl carbodiimide) in the mouse liver and kidneys. cAMP (10(-6) M) activated Na+, K+-ATPase in vitro reduced the activity of Mg2+-ATPase in the microsomal fraction, and did not change the activity of the mitochondrial ATPases in the mouse liver and kidneys. The following scheme of the mechanism of catecholamine (CA) effect on Na+, K+-ATPase is suggested: CA leads to beta-adrenoreceptors leads to adenylate cyclase leads to cAMP leads to protein kinase leads to Na+, K+-ATPase. The mechanism of Mg2+-ATPase regulation is discussed.
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PMID:[Catecholamine regulation of the liver and kidney ATPase activity in mice]. 627 63

The effect of different L-phenylalanine (Phe) concentrations (0.12-12.1 mM) on acetylcholinesterase (AChE), (Na+,K+)-ATPase and Mg2+-ATPase activities was evaluated in homogenates of suckling rat frontal cortex, hippocampus and hypothalamus. Phe, at high concentrations, reduced AChE activity in frontal cortex and hippocampus by 18%-20%. On the contrary, the enzyme activity was unaltered in the hypothalamus. Na+,K+-ATPase was stimulated by high levels of the amino acid, both in the frontal cortex and the hypothalamus by 60%, whereas it was inhibited in the hippocampus by 40%. Mg2+-ATPase was not influenced by Phe. It is suggested that: a) In the frontal cortex, the improper acetylcholine (ACh) release, due to AChE inhibition by Phe, combined with the stimulation of Na+,K+-ATPase, possibly explain tremor and the hyperkinetic behaviour in patients with classical phenylketonuria (PKU). b) In the hippocampus, inhibition of AChE by Phe could lead to problems in memory, while Na+,K+-ATPase inhibition by Phe may induce metabolic disorders and electrical instability of the synaptosomal membrane. c) In the hypothalamus, the behavioral problems in PKU "off diet" may be related to noradrenaline (NA) levels, which are probably correlated with the modulated Na+,K+-ATPase by Phe.
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PMID:Effects of L-phenylalanine on acetylcholinesterase and Na+,K+-ATPase activities in suckling rat frontal cortex, hippocampus and hypothalamus. 1192 33