Question

Uncontrolled action of which of the following enzymes plays a major etiological role in chronic myeloid leukemia?

• A. Tyrosine kinase
• B. Cholinesterase
• C. Galactokinase
• D. Bradykinin

Hint:

Think of the BCR-ABL fusion protein created by the Philadelphia chromosome.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
We need to identify the enzyme whose uncontrolled activity drives the development of chronic myeloid leukemia.

Step 2: Key Formula or Approach:
Chronic myeloid leukemia is caused by a specific chromosomal translocation that fuses two genes together, creating an abnormal protein with continuously active enzyme function that drives uncontrolled cell division.

Step 3: Detailed Explanation:
The Philadelphia chromosome, formed by a translocation between chromosomes 9 and 22, fuses the BCR gene with the ABL gene, creating the BCR-ABL fusion protein. This fusion protein is a constitutively active tyrosine kinase, meaning it is permanently switched on regardless of normal regulatory signals, continuously driving the growth signaling pathways that cause the uncontrolled proliferation of myeloid cells seen in chronic myeloid leukemia.
Cholinesterase is an enzyme that breaks down acetylcholine at nerve synapses and neuromuscular junctions and has no role in the pathogenesis of leukemia.
Galactokinase is involved in galactose metabolism, and its deficiency causes a form of galactosemia, unrelated to leukemia.
Bradykinin is actually a peptide, not an enzyme, involved in inflammation and blood pressure regulation, and it has no role in causing chronic myeloid leukemia.

Step 4: Final Answer:
So the enzyme whose uncontrolled action plays the major etiological role in chronic myeloid leukemia is tyrosine kinase, through the BCR-ABL fusion protein.