High-affinity calcium-stimulated, magnesium-dependent adenosine triphosphatase in Trypanosoma cruzi.
1. A high-affinity (Ca2+ + Mg2+)-ATPase and a low-affinity Mg(2+)-ATPase were identified in the 105,000 g fraction from epimastigote forms of Trypanosoma cruzi, the agent of Chagas' disease (Tulahuen strain). 2. Activities were conserved after enzyme solubilization with deoxycholate. 3. The Ca(2+)-stimulated ATPase activity was (a) lower than that of the Mg(2+)-ATPase; (b) inhibited by p-chloromercurobenzoate and orthovanadate and (c) insensitive to oligomycin. 4. Optimal stimulation by Ca2+ was observed at pH 6.5-6.8 in the presence of 1 mM MgCl2 and 0.1 M KCl. 5. The Mg(2+)-ATPase was insensitive to p-chloromercurobenzoate and orthovanadate and did not require KCl for activity. 6. Kinetic analysis of the (Ca2+ + Mg2+)-ATPase yielded a half-maximal stimulating concentration of 1.1 microM for Ca2+ and a Km of 66 microM for ATP. 7. The (Ca2+ + Mg2+)-ATPase clearly differed from the Ca(2+)- or Mg(2+)-ATPases previously characterized in the same strain of T. cruzi (Frasch et al., 1978; Comp. Biochem. Physiol. 60B, 271-275).
Cataldi de Flombaum
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Departamento de Química Biológica, Facultad de Medicina, Buenos Aires, Argentina.
Stoppani
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AO
D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000032:analysis* / Q000037:antagonists & inhibitors; D002729:Chloromercuribenzoates / Q000494:pharmacology; D003840:Deoxycholic Acid; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009840:Oligomycins / Q000494:pharmacology; D013347:Subcellular Fractions / Q000201:enzymology; D014349:Trypanosoma cruzi / Q000201:enzymology*; D014638:Vanadates / Q000494:pharmacology; D020245:p-Chloromercuribenzoic Acid
D002729:Chloromercuribenzoates; D009840:Oligomycins; D003840:Deoxycholic Acid; D014638:Vanadates; D020245:p-Chloromercuribenzoic Acid; D017301:Ca(2+) Mg(2+)-ATPase