Question

A 2-week-old baby presented with vomiting, acidosis, early cataract. Which of the following enzyme is defective?

• A. Galactose-1-phosphate uridyl transferase
• B. Galactokinase
• C. Hexokinase
• D. Aldol reductase

Hint:

In galactosemia, the defect in galactose-1-phosphate uridyl transferase leads to the accumulation of galactose and its metabolites, which cause cataracts, liver damage, and other systemic symptoms.

Answer 1

The Correct Option is A

To determine the defective enzyme in a 2-week-old baby presenting with vomiting, acidosis, and early cataract, we need to understand the metabolic pathway involved: the metabolism of galactose.

Galactose is converted into glucose-1-phosphate via the Leloir pathway. This pathway involves several key enzymes:

1. Galactokinase - Catalyzes the phosphorylation of galactose to galactose-1-phosphate.
2. Galactose-1-phosphate uridyl transferase (GALT) - Converts galactose-1-phosphate and UDP-glucose into UDP-galactose and glucose-1-phosphate.
3. UDP-galactose-4-epimerase - Converts UDP-galactose back to UDP-glucose, thus completing the cycle.
4. Aldol reductase and Hexokinase are not directly part of the galactose metabolism; aldol reductase is involved in converting glucose to sorbitol.

In this scenario, the presence of symptoms such as vomiting, acidosis, and cataracts indicates a defect in the utilization of captured galactose-1-phosphate, pointing towards a classical type of Galactosemia. This condition is caused by a deficiency in the Galactose-1-phosphate uridyl transferase (GALT) enzyme.

Conclusion: The enzyme Galactose-1-phosphate uridyl transferase is defective in this case, causing the characteristic symptoms to manifest due to the buildup of galactose-1-phosphate and galactose.