Partial characterization and effect of omeprazole on ATPase activity in Helicobacter pylori by using permeabilized cells.

ATPase activity in permeabilized cells of Helicobacter pylori as well as those of Helicobacter felis and Campylobacter jejuni was analyzed. The ATPase activities in these cells were most susceptible to sodium azide, fluoroaluminate, and dicyclohexylcarbodiimide, which are typical inhibitors of F ATPases. Optimal values for maximal activity were found to be at approximately pH 6.4, 6.0, and 6.0 for C. jejuni, H. pylori, and H. felis, respectively. The substituted benzimidazole compounds omeprazole, lansoprazole, and Eisai 3810 were found to have no effect on the F ATPase activity of H. pylori at concentrations which are inhibitory for cell growth (MICs). In addition, an extracellular, vanadate-susceptible ATPase activity was detected in H. pylori, which was also relatively insusceptible to the benzimidazole compounds. Thus, the mechanism of killing mediated by omeprazole and related compounds in Helicobacter pylori does not appear to be due to diminished ATPase activity.