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)

Treatment of liver plasma membranes with phospholipase A2 or high doses of concanavalin A enhances the activity of Mg2+ATPase assayed at temperatures greater than 30 degrees C. The effects of the two treatments are not additive. Both the removal of phospholipids and binding of the lectin increase the degree of polarization of fluorescence of the lipid-soluble fluorophores, diphenylhexatriene and beta-parinaric acid, suggesting that decreased lipid fluidity may activate Mg2+-ATPase. In fact modification of lipid fluidity by reconstitution of phospholipase-treated membranes with phosphatidylcholines of defined fatty acid composition or by addition of cis-vaccenic acid showed a strong inverse correlation between Mg2+ATPase activity and lipid fluidity as monitored by fluorescence polarization. However, despite the ability of concanavalin A to nonspecifically order membrane lipid, its effect on Mg2+ATPase is apparently not mediated in this manner because other enzyme-activating lectins such as Ricinus communis agglutinin and wheat germ agglutinin are without effect on lipid fluidity. The facts that lectins of lower valency than tetravalent native concanavalin A such as divalent succinyl concanavalin A are far less effective in activating the enzyme and that paraformaldehyde treatment also activates suggests that cross-linking of membrane proteins is responsible. Hence, the diminution in activity of this membrane enzyme due to the disordering effect of heat in the physiological temperature range can be counteracted by isothermally increasing the order of either membrane lipid or protein.
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PMID:Ordering of bulk membrane lipid or protein promotes activity of plasma membrane Mg2+ATPase. 610 59

Non-neurotoxic phospholipase A2 of Formosan cobra venom possessed higher hydrolytic activity on phosphatidylcholine vesicles and also had higher inhibitory action on Na+-K+-ATpase and Mg2+-ATPase of the rat synaptic membrane than neurotoxic beta-bungarotoxin of Formosan Krait Venom. Na+-K+-ATPase was more susceptible than Mg2+-ATPase to the inhibitory action of toxins, especially in the presence of Triton X-100. The inhibition of ATPases by toxins followed the Michaelis-Menton equation. It is interesting that various phospholipids and ions influenced phospholipase A2 and beta-bungarotoxin inhibition of ATPases. Sphingomyelin antagonized phospholipase A4 more profoundly than beta-bungarotoxin, while egg lecithin had the reverse effect. Both phosphatidylethanolamine and phosphatidylserine protected Na+-K+-ATPase from the inhibitory action of phospholipase A2 but not that of beta-bungarotoxin. High K+ (30 mM) did not affect, while Ca2+ (0.2 mM) decreased, the inhibitory action of phospholipase A2 on Na+-K+-ATPase; in contrast, high K+ reversed, and Ca2+ increased, that of beta-bungarotoxin. These findings imply that phospholipase A2 and beta-bungarotoxin may have different substrate specificities and prefer different conformational states of the membrane for binding. This may explain, at least in part, why beta-bungarotoxin is neurotoxic, while phospholipase A2 is not.
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PMID:Effects of beta-bungarotoxin and phospholipase A2 from Naja naja atra snake venom on ATPase activities of synaptic membranes from rat cerebral cortex. 612 64