Characteristics of ATPases Present in Everted Membrane Vesicles of Helicobacter pylori

Everted membrane vesicles of Helicobacter pylori were prepared and the membrane-resided ATPases were characterized. For comparison, Escherichia coli membrane ATPases and hog gastric mucosal H,K-ATPase were employed. ATPase assay revealed that the composite enzyme pool was relatively low in specific activities, below 1/10 times than that found in E. coli. According to their inhibitory specificities, most of the ATPase pool appeared to belong to the P-type ATPase, sensitive to vanadate but not to azide. The enzyme pool was extraordinarily resistant against treatment by N,N'-dicyclohexylcarbodiimide (DCCD). Certain monovalent cations, e.g., $K^+$ or $NH_4^{+}$ stimulated the whole enzyme pool only in the presence of $Mg^{2+}$. On the contrary, $Ni^{2+}$ and $Zn^{2+}$ increased enzyme activity rather effectively without the aid of $Mg^{2+}$. Under a defined condition employed, H. pylori cells could retain the membrane ATPase pool to the extent of $17{\%}$ at pH 3.2. Moreover, its activity was most stable in acidic conditions (pH 5.4-6.4). However, cytoplasmic or peripheral ATPase pools were hardly detected under acidity (below pH 4.6).