Mousy urine in a child is due to defect in conversion of phenlylalanine to –
**Core Concept**
Phenylketonuria (PKU) is an inborn error of metabolism characterized by the inability to convert phenylalanine (Phe) to tyrosine (Tyr) due to a deficiency in the enzyme phenylalanine hydroxylase (PAH). This enzyme catalyzes the hydroxylation of phenylalanine to form tyrosine.
**Why the Correct Answer is Right**
The correct answer is related to the defective enzyme responsible for converting phenylalanine to tyrosine. Phenylalanine hydroxylase is a crucial enzyme in the metabolism of amino acids, and its deficiency leads to the accumulation of phenylalanine in the body, causing various neurological and developmental problems. The enzyme requires tetrahydrobiopterin (BH4) as a cofactor for its activity. **Option C** is the correct answer because it is the enzyme responsible for converting phenylalanine to tyrosine.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it is not directly involved in the conversion of phenylalanine to tyrosine.
* **Option B:** This option is incorrect because it is not the primary enzyme responsible for the conversion of phenylalanine to tyrosine.
**Clinical Pearl / High-Yield Fact**
PKU is a genetic disorder that can be detected through newborn screening programs. Early diagnosis and treatment can prevent the development of intellectual disability and other complications associated with PKU.
**Correct Answer:** C. phenylalanine hydroxylase