Novel microsomal anion-sensitive Mg2+-ATPase activity in rat brain.
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.
Inagaki
C
C
Tanaka
T
T
Hara
M
M
Ishiko
J
J
D000251:Adenosine Triphosphatases / Q000032:analysis* / Q000037:antagonists & inhibitors; D000818:Animals; D027321:Anion Transport Proteins; D000838:Anions; D001921:Brain / Q000201:enzymology*; D017301:Ca(2+) Mg(2+)-ATPase; D002712:Chlorides / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004976:Ethacrynic Acid / Q000494:pharmacology; D005260:Female; D006863:Hydrogen-Ion Concentration; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013379:Substrate Specificity
D027321:Anion Transport Proteins; D000838:Anions; D002712:Chlorides; D004492:Edetic Acid; D000251:Adenosine Triphosphatases; D017301:Ca(2+) Mg(2+)-ATPase; C031652:anion-sensitive ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D004976:Ethacrynic Acid