A. Ottlecz et al., PHOSPHOLIPASE-ACTIVITY OF HELICOBACTER-PYLORI AND ITS INHIBITION BY BISMUTH SALTS - BIOCHEMICAL AND BIOPHYSICAL STUDIES, Digestive diseases and sciences, 38(11), 1993, pp. 2071-2080
In this study we measured phospholipase A (PLA) and C (PLC) activity o
f media filtrates and French Press lysates of the gastritis-inducing b
acteria Helicobacter pylori. We report here that both H. pylori lysate
s and filtrates contain PLA1, PLA2, and C enzymes, which readily hydro
lyze a radiolabeled dipalmitoylphosphatidylcholine (DPPC) and phosphor
ylcholine substrates, respectively. The specific activity of both PL4
and C enzymes were greatest in the 6.5-7.0 and 8.4-8.8 pH ranges, resp
ectively. Colloidal bismuth subcitrate (CBS) induced a dose-dependent
inhibition of PLA2 and C activity of both H. pylori lysates and filtra
tes. This inhibitory effect of CBS on PLA2 was antagonized in a dose-d
ependent fashion by the addition of CaCl2 to the incubation mixture, s
uggesting that calcium and bismuth may be competing for the same site
on the enzyme. In contrast, the ability of bismuth salts to inhibit PL
C activity of H. pylori lysates was not antagonized by CaCl2. Employin
g a biophysical assay system for surface wettability, it was determine
d that H. pylori lysates had the capacity to remove a synthetic phosph
olipid monolayer off a glass in a dose-dependent fashion. This ability
of the bacterial lysates to catalyze the transformation of a hydropho
bic surface to a wettable state was significantly attenuated in the pr
esence of bismuth salts. Our experimental results are, therefore, cons
istent with the possibility that H. pylori colonization compromises th
e stomach's barrier to acid by eroding a phospholipid lining, possibly
a monolayer, on the surface of the gastric mucus gel and that this pr
ocess is blocked in response to bismuth therapy.