Solubilization and kinetic characterization of mitochondrial adenosine triphosphatase from Leishmania donovani promastigotes.

Oligomycin-sensitive particulate ATPase (MB ATPase) from L. donovani promastigotes was solubilized by chloroform treatment. Polyacrylamide gel electrophoresis revealed several protein bands, with the major one possessing ATPase activity. The solubilized enzyme had Mg2+-ATPase and Ca2+-ATPase but no K+-dependent alkaline phosphatase activity. The Mg2+-ATPase activity was stimulated by monovalent cations and was not sensitive to oligomycin. Hence it is referred to as F1 ATPase. It had optimum activity at pH 7.6 and 30 degrees C. The Arrhenius plot for MB ATPase was biphasic with activation energies (Ea) of 16.2 and 3.4 kcal mol-1, while F1 ATPase exhibited a linear plot with Ea = 10.1 kcal mol-1. Lineweaver-Burk plots were biphasic with Km values of 0.17 and 1.25 mM for MB ATPase and 0.18 and 1.33 mM for F1 ATPase. The enzyme could be preserved at -15 degrees C in Tris-SO2-(4)-EDTA-ATP-glycerol (t1/2 = 20 days).