Properties and Drug Sensitivity of Adenosine Triphosphatases from Schistosoma mansoni

Abstract

The hydrolysis of ATP was measured in the presence of schistosome homogenates and various cations. The enzyme was stimulated strongly by either Ca2+ or Mg2+. Na+ added to the activation by Ca2+. A minor (17%) component was Na+ + K+ + Mg2+-dependent and ouabain-sensitive. Praziquantel, niridazole, oxamniquine, and hycanthone had no direct effect on the ATPase activity of schistosome homogenates. When schistosomes were pretreated with these drugs in vitro, washed thoroughly, and then homogenized, hycanthone, praziquantel, and oxamniquine caused a reduction in ATPase content of the worms. Niridazole did not share this effect. These results suggest that antischistosomal drugs did not directly inhibit ATPase, but did reduce ATPase in whole worms, possibly by removing or damaging the tegument, which is thought to contain most of the ATPase activity. In vitro ATPase measurements may be a useful indicator of pharmacologic activity of some types of drugs.

Schistosoma mansoni Ca2+-ATPase SMA2 Restores Viability to Yeast Ca2+-ATPase-deficient Strains and Functions in Calcineurin-mediated Ca2+Tolerance

“…Gradients were fractionated from the top to bottom, manually, in 1-ml aliquots (fractions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] that were stored at Ϫ70°C.…”

“…Ca 2ϩ -stimulated, Mg 2ϩ -dependent ATPase activity has been found in S. mansoni tissue homogenates (13) and microsomal fractions (14), which is coupled with an active transport of calcium (15). However, a correlation between this ATPase activity and specific Ca 2ϩ -ATPase isoforms has not been established.…”

Control of calcium homeostasis in Schistosoma mansoni

“…Although a small Na + ,K + -ATPase activity had already been reported in S. mansoni homogenate (Nechay et al 1980), we initiated our studies by re-investigating this enzyme due to its importance for maintaining membrane potential, sodium gradient and, indirectly, intracellular calcium concentrations (Sweadner 1989). The presence of Na + , K + -ATPase activities with different sensitivity to ouabain in tegumental and carcass preparations (Noël & Soares de Moura 1986) and the characterization of two classes of [ 3 H]ouabain binding sites in the homogenate (Pardon & Noël 1994) let us propose the existence of more than one isoenzyme in this worm, just as in mammals.…”

A Ca2+ ‐stimulated, Mg2+ ‐dependent ATPase activity in subcellular fractions from Schistosoma mansoni

“…Previous data on the presence of CaZ+-ATPase activity in S. mansoni consist of reports on the presence of ATPases activated by high concentrations of Ca 2+ or Mg 2+ [2][3][4][5] and of histochemical observations revealing ATPase activity in the tegument [14,15]. These ATPase activities referred to basic ATPases are probably not coupled to Ca 2+ transport.…”

“…In contrast to extensive studies in mammals, the information available on CaE+-ATPase activity in Schistosoma mansoni is limited to a few descriptions of ATPases activated by high concentrations of Ca 2+ or Mg 2+ [2][3][4]. Recently we also reported the presence of ATPase activity in the tegument of S. mansoni that required calcium or magnesium and had a Ko.5 of 0.32 mM for either of the metal-ATP complexes [5].…”