Question

Glucose transporter present in liver and pancreatic \(\beta\) (beta) - cell

• A. GLUT-1
• B. GLUT-2
• C. GLUT-3
• D. GLUT-4

Hint:

GLUT Isoforms:
GLUT-1 = RBCs/BBB; GLUT-2 = Liver & Pancreatic $\beta$-cells (Glucose sensor); GLUT-3 = Neurons; GLUT-4 = Skeletal muscle & Adipose (Insulin-dependent).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Facilitative glucose transporter (GLUT) isoforms exhibit tissue-specific expression and distinct kinetic Michaelis constants ($K_m$).
Key Formula or Approach:
\[ \text{GLUT-2: High } K_m \approx 15-20\text{ mM (Low Affinity, High Capacity Bidirectional Flux)} \]

Step 2: Detailed Explanation:
GLUT isoform tissue distribution and kinetic properties:
1. GLUT-1: Ubiquitous (erythrocytes, blood-brain barrier; low $K_m \approx 1\text{ mM}$).
2. GLUT-2: Expressed in Hepatocytes (liver), Pancreatic $\beta$-cells, renal tubular cells, and small intestinal basolateral membrane. Possesses a high $K_m$ ($\approx 15 - 20\text{ mM}$), allowing proportional bidirectional glucose flux at physiological and postprandial glucose levels to function as the physiological glucose sensor for insulin release.
3. GLUT-3: Neurons/brain (low $K_m$).
4. GLUT-4: Insulin-responsive transporter in skeletal muscle and adipose tissue.

Step 3: Final Answer:
Therefore, the glucose transporter in liver and pancreatic beta-cells is GLUT-2, matching option (B).