Phenylketonuria (PKU) Flashcards
1
Q
PKU is the most
A
common inborn error of amino acid metabolism 1 in 15,000 births
2
Q
inheritance pattern
A
autosomal recessive
- affected gene is on chromosome 12
3
Q
PKU is caused by a
A
deficiency in phenylalanine hydroxylase
4
Q
deficiency in phenylalanine hydroxylase causes
A
accumulation of phenylalanine in tissue, plasma and urine
5
Q
what is found in the urine which gives it a musty smell
A
phenylketones
6
Q
outline the phenylketonuria in a flow diagram
A
- Dietary protein and endogenous protein are good source of phenylalanine
- Deficiency in phenylalanine hydroxylase meaning phenylalalnine cannot be converted to tyrosin
- Phenylalanine accumulates in the blood
- Some phenylalanine is transaminated to phenylpyruvate which is converted to phenylacetate and phenyllactate–> accumulation of phenylketones
7
Q
other pathways affected by phenylalanine hydroxylase deficiency
A
those that use tyrosine
- Noradrenaline
- Adrenaline
- Dopamine
- Melanin
- Thyroid hormone
- Protein synthesis
8
Q
symptoms
A
• Severe intellectual disability
- Developmental delay
- Microcephaly (small head)
- Seizures
- Hypopigmentation
9
Q
transamination
A
transfer of an amino group to a keto acid w
whereas deamination is is the removal of an amino group.
10
Q
effect on brain development
A
- Phenylalanine is a large neutral amino acid (LNAA)
- Competes for transport across the blood brain barrier via Large Neutral Amino Acid Transporter (LNAAT)
- Excess phenylalanine can saturate this transporter
- Levels of other LNAA in the brain
- decreased
- Protein/neurotransmitter synthesis inhibited
- Brain development affected
- Causes mental retardation
11
Q
treatment
A
- Strictly controlled low phenylalanine diet
- Avoid artificial sweeteners (these contain
- phenylalanine)
- Avoid high protein foods such as:
- Meat
- Milk
- Eggs
12
Q
A
