Question

Which of the following statements about Phenylketonuria (PKU) are TRUE?

I. Individuals with PKU will be deficient in the synthesis of Tyrosine

II. Untreated PKU causes a serious reduction in Phenylalanine levels causing developmental abnormalities.

III. Defects in Phenylalanine hydroxylase often lead to the loss of enzyme stability resulting in degradation by the Ubiquitin/Proteasome System.

Choose the correct answer:

I, II, and III

I and III

I and II

I only

II and III

Answer 1

Answer is I and III because in phenlyketonuria the individuals will be deficient of synthesis of tyrosine due to the lack of PAH to breakdown phenylalanine were as the defect in PAH leads to loss of enzyme stability and undergo ubiquitin/proteasome system to degrade the mutant enzyme.

Why not the II because in phenlyketonuria the individual will lack the enzyme PAH which breakdown the phenylalanine to tyrosine, so synthesis does not happen there by, there will be ELEVATED levels of phenylalanine leading to development abnormalities.

Thankyou...