Alkaline phosphatase and ATPases in brush-border membranes of rat jejunum: distinct effects of divalent cations and of some inhibitors.
The effects of divalent cations and of some inhibitors on the activities of alkaline phosphatase and ATPase were examined in rat jejunal brush-border membranes (BBM) isolated by tha Ca(2+)-(BBMCa) or the Mg(2+)-precipitation method (BBMMg). Similar results were found in BBMCa and BBMMg though generally higher in BBMCa. Alkaline phosphatase activity was stimulated by 5 mM MgCl2 (30% to 44%), but not by 5 mM CaCl2 or 0.1 mM ZnCl2, at pH 9.5 or 7.4. ATPase activity was equally stimulated by 5 mM MgCl2 and by 5 mM CaCI2 (about 150%). Alkaline phosphatase activity was significantly inhibited by 1 mM vanadate, 5 mM diamox, 5.0 mM L-leucine and 1 mM theophylline. In contrast, Ca(2+)-ATPase and Mg(2+)-ATPase activities were not depressed by those alkaline phosphatase inhibitors, but were inhibited by 0.1 mM trifluoperazine (more than 70%). 0.1 mM ZnCl2 also appeared to be inhibitory to Ca(2+)-ATPase and Mg(2+)-ATPase, but not to alkaline phosphatase activity even in the presence of Ca2+ and Mg2+. These results suggest that Ca(2+)-ATPase and Mg(2+)-ATPase activities of the rat jejunal BBM are not merely manifestations of alkaline phosphatase, but rather belong to (a) distinct enzyme(s).
Wang
H
H
Laboratory of General and Comparative Biochemistry, University of Liège, Belgium.
Gilles-Baillien
M
M
D000086:Acetazolamide / Q000494:pharmacology; D000469:Alkaline Phosphatase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D002413:Cations, Divalent; D002712:Chlorides / Q000494:pharmacology; D007583:Jejunum / Q000201:enzymology* / Q000648:ultrastructure; D007930:Leucine / Q000494:pharmacology; D015636:Magnesium Chloride / Q000494:pharmacology; D008297:Male; D008871:Microvilli / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D013806:Theophylline / Q000494:pharmacology; D014268:Trifluoperazine / Q000494:pharmacology; D014638:Vanadates / Q000494:pharmacology; D015032:Zinc / Q000494:pharmacology; D017967:Zinc Compounds
D002413:Cations, Divalent; D002712:Chlorides; D017967:Zinc Compounds; D015636:Magnesium Chloride; D014268:Trifluoperazine; D014638:Vanadates; C016837:zinc chloride; D013806:Theophylline; D000469:Alkaline Phosphatase; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D007930:Leucine; D015032:Zinc; D002122:Calcium Chloride; D000086:Acetazolamide