Three aspecific ATPases in Trichomonas vaginalis.

1. Three aspecific ATPases were found in the sedimentible fractions of Trichomonas vaginalis. 2. One, with a pH optimum of 5.5, was equally activated by Ca2+ or Mg2+, moderately stable, preferred nucleotide diphosphates as substrates, and was inhibited by vanadate, oligomycin, nitrate and Na+. 3. A second, with a pH optimum of 7.5, was activated by Mg2+, preferred guanosine diphosphate as substrate, and was the least stable and most subject to inhibitors (vanadate, oligomycin, NEM, NBD-Cl, azide and Cl-). 4. The third, pH optimum 8.0, was activated by Ca2+, was latent and the most stable, reacted equally well with nucleotide tri- or diphosphates, and was the least susceptible to inhibitors (vanadate and NEM). 5. All exhibited proton-translocating ability.