Question

Proton pump inhibitors act by inhibiting:

• A. \(\text{H}^+ / \text{K}^+ \text{ ATPase enzyme}\)
• B. \(\text{H}^+ / \text{Na}^+ \text{ pump}\)
• C. \(\text{H}^+ / \text{K}^+ \text{ pump}\)
• D. \(\text{H}^+ / \text{ATPase enzyme}\)

Hint:

PPI Mechanism: PPIs covalently bind to and irreversibly inhibit the active $\text{H}^+/\text{K}^+$-ATPase enzyme system, blocking the final common pathway of gastric acid production.

Answer 1

The Correct Option is A

Concept: Gastric acid secretion by parietal cells in the stomach mucosa is driven by a specialized primary active transport system called the proton pump. The formal biochemical designation for this proton pump is the $\text{H}^+/\text{K}^+$-ATPase enzyme. This enzyme uses energy from ATP hydrolysis to pump hydrogen ions ($\text{H}^+$) out into the gastric lumen in exchange for potassium ions ($\text{K}^+$).

Step 1: Analyze how Proton Pump Inhibitors work.
Proton Pump Inhibitors (PPIs), such as omeprazole, lansoprazole, and pantoprazole, are prodrugs that accumulate in the acidic canaliculi of parietal cells. There, they are converted into active sulfenamide intermediates that form a covalent disulfide bond with sulfhydryl groups on the $\text{H}^+/\text{K}^+$-ATPase enzyme. This produces irreversible inhibition of gastric acid secretion. While option C mentions the "pump," option A provides the precise, structurally correct enzymatic term ($\text{H}^+/\text{K}^+$-ATPase enzyme).