Enzyme defect in galactosemia ?
**Core Concept**
Galactosemia is a genetic disorder characterized by the inability to metabolize the sugar galactose, which is a component of lactose in milk. This condition is caused by a deficiency of an enzyme involved in the galactose metabolism pathway.
**Why the Correct Answer is Right**
The enzyme defect in galactosemia is due to a deficiency of galactose-1-phosphate uridyltransferase (GALT). This enzyme catalyzes the conversion of galactose-1-phosphate to glucose-1-phosphate, a crucial step in the metabolism of galactose. Without sufficient GALT activity, galactose-1-phosphate accumulates and causes damage to the liver, kidneys, and brain. The genetic mutations that lead to galactosemia often result in a non-functional GALT enzyme.
**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not specify the enzyme involved in galactose metabolism. While galactokinase is an enzyme involved in galactose metabolism, it is not the primary enzyme deficient in galactosemia.
**Option B:** is incorrect because it mentions a different enzyme, galactose-4-epimerase, which is not directly involved in the primary metabolic pathway affected in galactosemia.
**Option C:** is incorrect because it does not accurately identify the enzyme defect in galactosemia. While galactose-1-phosphate uridyltransferase is the correct enzyme, option C does not provide a clear or concise answer.
**Clinical Pearl / High-Yield Fact**
Galactosemia is often diagnosed through a newborn screening test, which detects elevated levels of galactose-1-phosphate in the blood. Early detection and treatment with a galactose-free diet can prevent long-term complications and improve outcomes for individuals with galactosemia.
**Correct Answer:** C. Galactose-1-phosphate uridyltransferase.