Which of the following metabolic disorders is characterized by an inability to convert phenylalanine to tyrosine due to a deficiency of the enzyme phenylalanine hydroxylase?

A Maple syrup urine disease
B Phenylketonuria ✓
C Homocystinuria
D Tyrosinemia

Explanation

Phenylketonuria (PKU) is a genetic disorder caused by a deficiency of the enzyme phenylalanine hydroxylase, which is necessary for the conversion of phenylalanine to tyrosine. If left untreated, PKU can lead to intellectual disability and other serious health problems.

Mnemonic

'P'henylalanine 'K'eeps 'U'ntreated = PKU

Source

Nelson Textbook of Pediatrics
Metabolic and Nutritional Disorders Genetic Metabolic Disorders Amino Acid Metabolism Hard MEDICAL Confidence: high