<prompt> Which of the following is a Protein Pump Inhibitor?RanitidineMisoprostolOmeprazoleLaxatidine  <response>: Omeprazole is a proton pump inhibitor, it inhibits gastric acid secretion. It inhibits the H K ATPase enzyme in the apical membrane of parietal cells, thereby reducing acid secretion. Acid secretion resumes only when new H K ATPase is formed. It is the treatment of choice for peptic ulcer, gastroesophageal reflux disease, and Zollinger Ellison syndrome. Ref: Essentials of Medical Pharmacology By KD Tripathi, 5th Edition, Page 589 - 94. 