The document summarizes the gastric H+/K+ ATPase pump. It is located in the stomach's gastric mucosa and exchanges intracellular potassium for luminal hydrogen ions, pumping hydrogen ions out to produce gastric acid. The pump is made of alpha and beta subunits and uses ATP hydrolysis to actively transport ions against their concentration gradients, exporting either 2H+/2K+ or 1H+/1K+ per ATP. Inhibiting this pump decreases stomach acidity and is used to treat gastric ulcers.

1. ACTIVE TRANSPORT MEDIATED BY
ATP POWERED PUMPS
GASTRIC H+/K+ ATPase
Shruthi Shree Gandhi.S
I Msc biochemistry
SRI RAMAKRISHNA COLLEGE OF ARTS AND
SCIENCE FOR WOMEN

2. GASTRIC H+/K+ ATPase
• As the name implies the gastric H+/K+
ATPase is a P class ATP powered pump
found on the eukaryotic epithelial cells
located in the inner cell lining of stomach
called gastric mucosa. Some also present
in renal medulla.
• The gastric H+/K+ ATPase is a proton
pump of the stomach that exchanges
potassium from the intestinal lumen with
cytoplasmic hydronium.
• It is responsible for gastric acid secretion.

3. MECHANISM FOR GASTRIC ACID SECRETION

4. CO2 enters the cell and is catalyzed by the enzyme
carbonic anhydrase producing carbonic acid (H2CO3.)
carbonic acid dissociates in to bi carbonate ion
(HCO3)AND hydrogen ion.(H)
bicarbonate ion is exchanged for chloride ion entering
the cell and is known as chloride shift.
Structure of H+/K+ ATPase
Alpha subunit
Encoded by the atp4a gene
Made of 1000 aminoacids
Contains two active sites for the binding of hydronium ion
Contains phosphorylation site(asp385)
Beta subunit
Contains 300 amino acids
Encoded by the ATP4B gene
beta subunit involves in stabilizing alpha subunit and
is required for the function of the enzyme.

5. MECHANISM OF H+/k+
ATPase

6. • The H+/K+ ATPase transports ions against their
concentration gradient using energy obtained from
hydrolysis.
• The number of ions transported per ATP varies from
2H+/2K+ OR 1H+/1K+ depending on the pH of the stomach.
• The h+ ion bind to its binding site when the binding site is
exposed in to the cytoplasm of the mucosal cells and
released when the pump faces the lumen by utilizing ATP.
• The released h+ ion combines with cl- ion in lumen and
forms hcl.(gastric acid)
• When the pump faces the lumen after a conformational
change. the binding affinity for k+ is greater the k+ ion
binds to its binding site the pump undergoes
conformational changes and the pump now faces the
cytoplasm of the cell where the binding affinity for
potassium ion is low and is released in to the cell.
• Inhibiting the h+/k+ pump decreases stomach acidity and
is the method of treating gastric diseases like ulcer.

7. • Thank you