Helicobacter pylori urease was characterized by means of an enzyme histochemical electron microscopic technique. Ultrastructural analysis revealed no urease activity in one strain; in seven H. pylori strains (43.75%), urease activity was associated with the cell membrane. Eight strains (50.0%) showed reaction product located within the cytoplasm. Urease activity showed no correlation with localization of activity. Our results demonstrate that H. pylori urease is not uniform in all H. pylori strains, and differences in activity and localization of urease activity may account for different virulence activities.

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Inhibition of H. pylori urease was studied by means of electron-microscopy and electrophoretic methods using different urease inhibitors, such as acetohydroxamic-acid (AHA), L-ascorbic acid (AsA), copper ions, a combination of L-ascorbic acid with copper ions and UV light. AHA in two different concentrations and AsA at a concentration of 0.1 mg ml-1 showed incomplete inhibition of H. pylori urease activity in our electrophoretic experiments. Only membrane-bound activity was inhibited with AHA but not the activity localized within the cytoplasma as demonstrated by electron-microscopy. AsA at a concentration of 0.5 mg ml-1 and the combination of copper ions (1 microgram ml-1) with AsA completely inhibited the urease activity as demonstrated by electron-microscopy and electrophoretic experiments. Cu2+ ions in high concentrations (100 micrograms ml-1) and UV light exposure for more than 4 h induced a complete disintegration of H. pylori. Electrophoresis showed no active protein after UV light exposure of 2 h. Different urease inhibitors tested in this study showed dose-dependent inhibitory effects on H. pylori urease in vitro.

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