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)

Ethacrynic acid (EA) highly sensitive Mg2+-ATPase activity was demonstrated in rat brain microsomes. Marker enzyme studies suggested that the EA highly sensitive Mg2+-ATPase activity originated mainly from plasma membranes, and possibly from synaptic vesicles. Oligomycin did not affect the EA highly sensitive Mg2+-ATPase activity. Sulfhydryl reagents, such as N-ethylmaleimide and 5,5'-dithiobis-(2-nitrobenzoic acid), and anion transport inhibitors, such as 4-acetamide-4'-isothiocyanostilbene-2,2'-disulfonic acid, 4,4'-diisothiocyano-stilbene-2,2'-disulfonic acid and 2,4-dinitro-1-fluorobenzene, completely inhibited the EA highly sensitive Mg2+-ATPase activity with apparent Ki values at 5, 5, 8, 8 and 10 microM respectively. Treatment of microsomes with ethylenediaminetetraacetic acid and ammonium sulfate increased the EA highly sensitive Mg2+ and Na+,K+-ATPase activities, but not EA less sensitive Mg2+- or HCO3-ATPase activity, 2- to 3-fold that in crude microsomes. Relative substrate specificities of ATP much greater than GTP greater than ITP greater than UTP, CTP, a Km for ATP at 0.77 mM, and an optimal pH at pH 7.4 were observed. Among the anions tested (Cl-, Br-, F-, HCO3-, I-, SCN-, NO3-), EA highly sensitive Mg2+-ATPase activity was stimulated significantly by Cl- and reduced by NO3-. These data suggest that a novel, plasma membrane-located and anion-sensitive Mg2+-ATPase activity exists in the brain.
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PMID:Novel microsomal anion-sensitive Mg2+-ATPase activity in rat brain. 298 56

Membrane ghosts were prepared from purified lysosomes (tritosomes) of rat liver by hypo-osmotic treatment. Mg2+-ATP-driven acidification was observed in the membrane ghosts using acridine orange as a fluorescent probe of the transmembrane pH gradient (delta pH). Its properties were the same as those of intact lysosomes reported previously (Ohkuma, S., Moriyama, Y., & Takano, T. (1982) Proc. Natl. Acad. Sci. U.S. 79, 2758-2762; Moriyama, Y., Takano, T., & Ohkuma, S. (1982) J. Biochem. 92, 1333-1336). The H+-pump was found to be electrogenic with use of bis(3-phenyl-5-oxoisoxasol-4-yl)pentamethine oxonol as a fluorescent membrane potential probe. Alkaline Mg2+-ATPase activity was also identified on the membranes. It showed a pH maximum of pH 8.0-8.5, a Km value for ATP of 0.36 mM and a Vmax of 0.41 units/mg protein at 30 degrees C. Its activity was inhibited by dicyclohexylcarbodiimide, tri-n-butyltin, azide and ADP, but not by ouabain or vanadate. It differed from mitochondrial F1F0-ATPase in sensitivities to N-ethylmaleimide, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, quercetin, and oligomycin. Since this alkaline Mg2+-ATPase activity is very similar to the H+-pump activity in its requirement for divalent cations, substrate specificity and sensitivities to various chemicals, it may act as a proton translocase (H+-pump). Possible mechanisms of action of some chemicals, such as 4-acetamide-4'-isothiocyanatostilbene-2,2'-disulfonic acid, that inhibited the H+-pump but not the alkaline Mg2+-ATPase, are discussed.
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PMID:Proton translocating ATPase in lysosomal membrane ghosts. Evidence that alkaline Mg2+-ATPase acts as a proton pump. 614 4