Question:
Classic galactosemia is due to deficiency of which enzyme?
Classic galactosemia is due to deficiency of which enzyme?
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The classic, severe galactosemia is the GALT (uridyltransferase) defect, not galactokinase.
Updated On: Jun 24, 2026
- Galactose-1-phosphate uridyltransferase
- HGPRT
- Galactokinase
- Epimerase
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The Correct Option is A
Solution and Explanation
Step 1: Galactosemia is an autosomal recessive disorder of galactose metabolism in which a deficient enzyme prevents proper conversion of galactose (mainly from milk lactose) into glucose-1-phosphate.
Step 2: Classic (type I, most common and most severe) galactosemia is caused by deficiency of galactose-1-phosphate uridyltransferase (GALT). This causes toxic accumulation of galactose-1-phosphate, leading to vomiting, hepatomegaly, jaundice, cataracts, and E. coli sepsis in neonates.
Step 3: Because the question asks for the classic enzyme defect of galactosemia, option (a) GALT is correct.
Step 4: Galactokinase deficiency (c) is a milder variant causing mainly cataracts; epimerase deficiency (d) is the rarest variant; HGPRT (b) belongs to purine metabolism and is unrelated.
Step 2: Classic (type I, most common and most severe) galactosemia is caused by deficiency of galactose-1-phosphate uridyltransferase (GALT). This causes toxic accumulation of galactose-1-phosphate, leading to vomiting, hepatomegaly, jaundice, cataracts, and E. coli sepsis in neonates.
Step 3: Because the question asks for the classic enzyme defect of galactosemia, option (a) GALT is correct.
Step 4: Galactokinase deficiency (c) is a milder variant causing mainly cataracts; epimerase deficiency (d) is the rarest variant; HGPRT (b) belongs to purine metabolism and is unrelated.
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