Question

The hereditary defect phenylketonuria is caused by deficiency of

• A. Phenylalanine hydroxylase
• B. Fructokinase
• C. Glucokinase
• D. Haemoglobin reductase

Answer 1

Answer: (A)

Phenylalanine hydroxylase

Phenylketonuria (PKU) is an inherited error of metabolism caused by a deficiency in the enzyme phenylalanine hydroxylase. Loss of this enzyme results in mental retardation, organ damage and unusual posture. Classical PKU is an autosomal recessive disorder, caused by mutations in both alleles of the gene for phenylalanine hydroxylase.

So, the correct option is 'Phenylalanine hydroxylase'.