Phenylketonuria

Question 1

What results due to the enzyme deficiency in PKU?

Answer 1

Lack of tyrosine

Accumulation of phenylketones in blood

Question 2

What causes presence of phenylketones in blood in PKU?

Answer 2

Phenylalanine hydroxylase enzyme deficiency means phenylalanine builds up and is instead converted to phenylpyruvate in transamination reactions
Phenylpyruvate–> phenylketones

Question 3

List some symptoms of PKU

Answer 3

Seizures
Microcephaly (small head)
Hypopigmentation
Severe intellectual disability
Developmental delay

Question 4

Why does hypopigmentation occur in PKU?

Answer 4

Tyrosine is used to make melanin, the pigment in skin
Phenylalanine hydroxylase enzyme defect means no/less tyrosine
Therefore less pigmentation

Question 5

What is diagnosed/tested for in a heel prick test?

Answer 5

PKU
Homocystinuria
Cystic Fibrosis
Congenital hypothyroidism
Sickle cell disease

Question 6

What causes Phenylketonuria (PKU)?

Answer 6

Autosomal recessive

Defective phenylalanine hydroxylase enzyme

Question 7

How does PKU lead to developmental delay?

Answer 7

Lack of ….enzyme
Accumulation of phenylpyruvate which inhibits pyruvate uptake into mitochondria
Therefore affects energy metabolism in brain

Question 8

Treatment for PKU?

Answer 8

Low phenylalanine diet

Avoid high protein foods

Question 9

What is tyrosine essential for?

Answer 9

Synthesis of thyroid hormones
Melanin
Catecholamines ((nor) adrenaline)