A (Ca(2+)-Mg2+)ATPase from Schistosoma mansoni is coupled to an active transport of calcium.
The (Ca(2+)-Mg2+)ATPase activity in microsomes of Schistosoma mansoni is fully inhibited by vanadate (I50 = 2.5 microM). 45Ca2+ is accumulated within microsomal vesicles in an ATP-dependent process that is enhanced 5-fold in the presence of 40 mM phosphate. Accumulated 45Ca2+ is rapidly released by 5 microM of the Ca2+ ionophore A23187 (t1/2 less than or equal to 6 s). (Ca(2+)-Mg2+)ATPase activity and Ca2+ uptake share the same subcellular distribution pattern and similar Ca2+ sensitivities (K0.5 = 0.39 microM and 0.15 microM, respectively). The substrate selectivity is high for both ATPase activity and Ca2+ transport. These results indicate the presence of an active transport of Ca2+ coupled to the (Ca(2+)-Mg2+)ATPase activity previously described in this parasite. A plasma membrane localization and physiological role in calcium homeostasis are suggested.
Cunha
V M
VM
Departamento de Parasitologia e Biofísica Celular, Universidade Federal do Rio de Janeiro, Brazil.
Meyer-Fernandes
J R
JR
Noël
F
F
D000818:Animals; D001693:Biological Transport, Active; D017301:Ca(2+) Mg(2+)-ATPase / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000187:drug effects / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism; D008861:Microsomes / Q000201:enzymology / Q000378:metabolism; D012550:Schistosoma mansoni / Q000201:enzymology* / Q000378:metabolism; D013379:Substrate Specificity; D014638:Vanadates / Q000494:pharmacology
D014638:Vanadates; D017301:Ca(2+) Mg(2+)-ATPase; D000252:Calcium-Transporting ATPases; D002118:Calcium