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)

Concanavalin A inhibits the (Na+-K+)-ATPase activity of isolated rat-liver plasma membranes, while leaving the Mg2+-ATPase unaffected. Glucagon and cyclic AMP act supplementary to the lectin in the inhibition. The lectin effect is counteracted by insulin and L-epinephrine, and is completely abolished by the beta-adrenergic blocking agent propranolol. Results are discussed on the basis of the known interactions of concanavalin A with plasma membrane components, including its hormone-like action.
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PMID:Studies on plasma membranes. XXIII. Hormone-like action of concanavalin A on liver plasma membranes: inhibition of (Na+-K+)ATPase. 12 72

The adenylate cyclase activity from a rat liver plasma membrane preparation was inhibited by low concentrations (1-10 muM) of the mercurial diuretic mersalyl. Complete inhibition was obtained with 0.1 mM mersalyl. Similar effects were observed whether the adenylate cyclase preparation was assayed in the presence of 10 muM GTP, 0.1 muM glucagon, 10 mM NaF or without any addition. The effect of mersalyl was not due to inhibition of the regenerating system present in the incubation medium, since the effect of mersalyl was preserved and even enhanced in its absence. The inhibition brought about by mersalyl was due to both a decrease of the maximal velocity of the reaction and of the affinity of the enzyme for the substrate. It was immediate, and irreversible spontaneously, but it was reversed by the simultaneous additions of 2-mercaptoethanol, in a dose-dependent fashion. Other -SH reagents were found to have an effect equal to, or lower than, that of mersalyl. Mersalyl had no effect upon Mg2+-ATPase, although it inhibited the (Na+-K+) activated ATPase. Since mersalyl is known to be a 'non-penetrant' reagent, it is postulated that a catalytically important, mercurial-sensitive, part of adenylate cyclase is at the surface of the plasma membrane. This view is supported by the following facts: (a) mersalyl acted with a similar dose-response curve upon an intact as well as a detergent-dispersed cyclase preparation while no effect was observed upon a solubilized Mg2+-ATPase preparation; (b) a covalent p-chloromercuribenzoate-Sephadex preparation (but not its supernatant) inhibited the cyclase from intact membranes. It is proposed that mercurial derivatives, by their relative specificity of action (no effect on Mg2+-ATPase), can serve as useful probes in the elucidation of the multicomponent structure of the cyclase system.
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PMID:Adenylate cyclase from rat-liver plasma membrane: inhibition by mersalyl and other mercurial derivatives. 12 56

A high affinity Ca2+-stimulated, Mg2+-dependent ATPase (Ca2+-Mg2+-ATPase) was identified in microsomes and plasma membrane vesicles isolated from rat hepatocytes. The distribution of this enzyme was similar to that of the plasma membrane marker enzymes alkaline phosphodiesterase and 5'-nucleotidase. The Ca2+-Mg2+-ATPase had an apparent half-saturation constant of approximately 75 nM for Ca2+. After incubation of rat hepatocytes with 25 nM vasopressin for 3 min, the activity of Ca2+-Mg2+-ATPase was decreased 15-30%. The effect of vasopressin on the activity of this enzyme was near maximal after incubating hepatocytes with vasopressin for only 15 sec. The concentration of vasopressin needed for half-maximal inhibition of this enzyme in hepatocytes was approximately 6 nM. Treatment of the hepatocytes with 10 microM phenylephrine caused about a 10% decrease in ATPase activity while 10 nM glucagon or 200 microU/ml insulin did not affect the enzyme. These findings suggest that inhibition of the Ca2+-Mg2+-ATPase activity may be part of the mechanism by which vasopressin and alpha-adrenergic agonists elevate cytosolic Ca2+ in hepatocytes.
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PMID:Regulation of Ca2+-Mg2+-ATPase activity in hepatocyte plasma membranes by vasopressin and phenylephrine. 613 76

In the perfused rat liver administration of glucagon was shown to result in a transiently increased uptake of K+, indicating the possible involvement of the Na+, K+-ATPase. Direct measurement of the activity of Na+, K+-ATPase revealed a two-fold stimulation of the enzyme by glucagon. The effect of glucagon on the activity of the enzyme was immediate. Simultaneously with the increase in the activity of the Na+, K+-ATPase, the activity of Mg2+-ATPase decreased. In order to evaluate whether the activation of the Na+, K+-ATPase by glucagon is related to the metabolic effects of the hormone, experimental conditions known to interfere with the activity of the enzyme were employed and glucagon stimulation of Ca2+-efflux, mitochondrial metabolism and gluconeogenesis were measured. K+-free perfusate, high K+ perfusate or ouabain interfered to varying degrees with the glucagon stimulation of these responses. The combination of K+-free perfusate and ouabain almost completely abolished the glucagon stimulation of all three parameters. These results demonstrate the glucagon stimulation of Na+, K+-ATPase and raise the possibility that the activation of the enzyme by glucagon might be a necessary link for the manifestation of its metabolic effects.
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PMID:Glucagon stimulation of hepatic Na+, K+-ATPase. 628 3