Sites of reaction of the gastric H,K-ATPase with extracytoplasmic thiol reagents
Abstract
The vesicular gastric H,K-ATPase catalyzes an electroneutral H for K exchange allowing acidification of the intravesicular space. There is a total of 28 cysteines present in the alpha subunit of the gastric H,K-ATPase, of which 10 are found in the predicted transmembrane segments and their connecting loop, and 9 are present in the beta subunit, of which 6 are disulfide-linked. To determine which of these was accessible to extracytoplasmic attack, the enzyme was inhibited by four different substituted 2-pyridylmethylsulfinyl benzimidazoles, 5-methoxy-2-[(4-methoxy-3, 5-dimethyl-2-pyridyl)methylsulfinyl]-1H-benzimidazole (omeprazole), 2-[(4-trifluoroethoxy-3-methyl-2-pyridyl)methylsulfinyl]-1H-ben zimida zole (lansoprazole), 5-difluoromethoxy-2-[3, 4-methoxy-2-pyridyl)methylsulfinyl]-1H-benzimidazole (pantoprazole), and 2-[(4-(3-methoxypropoxy)-3-methyl)-2-pyridyl)methylsulfinyl]-1H-++ +benzi midazole (rabeprazole), under acid transporting conditions. All of these compounds are weak bases that accumulate in the acidic space generated by the pump and undergo an acid catalyzed rearrangement to a cationic sulfenamide, which forms disulfides with accessible cysteines. The relative rates of acid activation of these compounds corresponded to the relative rates of inhibition of ATPase activity and acid transport. Fragmentation of the enzyme by trypsin followed by SDS-polyacrylamide gel electrophoresis showed that omeprazole bound covalently to one of the two cysteines in the domains…
Read the paper
Related studies
- The Prediction of the In Vitro Release Curves for PLGA-Based Drug Delivery Systems with Neural Networks
- Promising Ursolic Acid as a Novel Antituberculosis Agent: Current Progress and Challenges
- Proof of principle concept for the analysis and functional prediction of rare genetic variants in the CYP2C19 and CYP2D6 genes
- Fabrication, characterization, and docking studies of furosemide-loaded nanosponges using the emulsion solvent diffusion method
- The Effect of Concomitant Administration of Proton Pump Inhibitors on the Pharmacokinetics of CDK4/6 Inhibitors in Rats: Implications for the Evaluation of Hepatic and Transporter-Mediated Drug–Drug Interactions
- Mining the Metabolic Capacity of Clostridium sporogenes Aided by Machine Learning
Go deeper in Evidence Hub
Evidence Hub adds a study data sheet (design, sample size, evidence level, key numbers), an AI summary and a chat grounded in the paper's text.