Solubilization and some properties of the Mg2+-activated adenosine triphosphatase from Trypanosoma cruzi.

1. Grinding of epimastigotes of Trypanosoma cruzi with glass powder in a mortar yielded a Mg2+-activated adenosine triphosphatase (ATPase) preparation which was highly sensitive to oligomycin. 2. Chloroform treatment of the particles resulted in the solubilization of an ATPase which was (a) activated by MgCl2; (b) slightly inhibited by CaCl2; (c) activated by sulphite and bisulphite; (d) had an optimum pH of 7.6; and (e) had a Km for ATP of 2.1 mM (in the presence of 4 mM MgCl2). 3. The solubilized enzyme was insensitive to oligomycin and leucinostatin, which inhibited the membrane-bound ATPase, though inhibited by efrapeptin and quercetin. 4. The results indicate that the chloroform-extracted enzyme is a soluble F1-ATPase similar to those isolated from mammalian mitochondria.