Ottlecz A, Romero J J, Hazell S L, Graham D Y, Lichtenberger L M
Department of Physiology and Cell Biology, University of Texas Medical School at Houston 77225.
Dig Dis Sci. 1993 Nov;38(11):2071-80. doi: 10.1007/BF01297087.
In this study we measured phospholipase A (PLA) and C (PLC) activity of media filtrates and French Press lysates of the gastritis-inducing bacteria Helicobacter pylori. We report here that both H. pylori lysates and filtrates contain PLA1, PLA2, and C enzymes, which readily hydrolyze a radiolabeled dipalmitoylphosphatidylcholine (DPPC) and phosphorylcholine substrates, respectively. The specific activity of both PLA and C enzymes were greatest in the 6.5-7.0 and 8.4-8.8 pH ranges, respectively. Colloidal bismuth subcitrate (CBS) induced a dose-dependent inhibition of PLA2 and C activity of both H. pylori lysates and filtrates. This inhibitory effect of CBS on PLA2 was antagonized in a dose-dependent fashion by the addition of CaCl2 to the incubation mixture, suggesting that calcium and bismuth may be competing for the same site on the enzyme. In contrast, the ability of bismuth salts to inhibit PLC activity of H. pylori lysates was not antagonized by CaCl2. Employing a biophysical assay system for surface wettability, it was determined that H. pylori lysates had the capacity to remove a synthetic phospholipid monolayer off a glass in a dose-dependent fashion. This ability of the bacterial lysates to catalyze the transformation of a hydrophobic surface to a wettable state was significantly attenuated in the presence of bismuth salts. Our experimental results are, therefore, consistent with the possibility that H. pylori colonization compromises the stomach's barrier to acid by eroding a phospholipid lining, possibly a monolayer, on the surface of the gastric mucus gel and that this process is blocked in response to bismuth therapy.
在本研究中，我们测定了致胃炎细菌幽门螺杆菌的培养基滤液和高压匀浆裂解物中的磷脂酶A（PLA）和C（PLC）活性。我们在此报告，幽门螺杆菌裂解物和滤液均含有PLA1、PLA2和C酶，它们分别能轻易水解放射性标记的二棕榈酰磷脂酰胆碱（DPPC）和磷酸胆碱底物。PLA和C酶的比活性分别在pH值6.5 - 7.0和8.4 - 8.8范围内最高。枸橼酸铋钾（CBS）对幽门螺杆菌裂解物和滤液的PLA2和C活性均产生剂量依赖性抑制。通过向孵育混合物中添加氯化钙，CBS对PLA2的这种抑制作用以剂量依赖性方式被拮抗，这表明钙和铋可能在酶的同一位点竞争。相比之下，氯化钙并未拮抗铋盐对幽门螺杆菌裂解物PLC活性的抑制能力。采用表面润湿性的生物物理测定系统，确定幽门螺杆菌裂解物能够以剂量依赖性方式从玻璃上去除合成磷脂单层。在铋盐存在下，细菌裂解物将疏水表面催化转化为可湿润状态的这种能力显著减弱。因此，我们的实验结果与以下可能性一致：幽门螺杆菌定植通过侵蚀胃黏液凝胶表面的磷脂内衬（可能是单层）来破坏胃对酸的屏障，并且铋治疗可阻止这一过程。
