Amino Acid Metabolism Defects Flashcards
There are a lot of inherited diseases involving defects in amino acid metabolism. What do they frequently lead to if untreated?and what does the treatment usually involve?
Untreated- intellectual impairment
Treatment- restricting specific amino acids in diet
What is the heel prick test and when it is done?
In new born babies
It is a test in which they screen for genetic diseases by taking a sample of blood.
They look for: PKU Maple syrup urine disease IVA Glutaric aciduria Homocystinuria
*these are inborn error of metabolism, other diseases are screened for
What is phenylketonuria?
Deficiency in phenylalanine hydroxylase (phenylalanine to tyrosine)
Leads to phenylalanine in tissue, plasma and urine
Accumulation of phenylketones in urine- musty smell
How do you treat the phenylketonuria?
Strictly control diet
Low phenylalanine diet
Avoid artificial sweeteners
Avoid high protein foods
What are the symptoms of PKU?
Server intellectual disability
Development delay
Microcephaly
Seizures
Hypopigmentation
** can all be avoided with early intervention
Why would pku result in the intellectual disability?
Because the lack of enzyme stopes phenylalanine being converted to tyrosine and this stops the production of noradrenaline and adrenaline, dopamine etc which has an impact of development
Tyrosine also effects protein synthesis and the thyroid hormones
What is homocystinurias?
Problems breaking down methionine
You have excess homocystine (oxidised form of homocysteine) excreted in urine
Autosomal recessive
Defect in cystathionine B-synthase most common (CBS)
Affects connective tissue, muscle, CNS, CVS
What is the treatment of homocystinurias?
Low methionine diet
Avoid milk meat fish cheese and eggs
Nuts and peanut butter too
Cysteine. Vit b6, betaine, b12 and folate supplement
Why does PKU cause an increase in SERUM phenylalanine and the production of phenylpyruvate?
Tyrosine is needed for the production of neurotransmitters (noradrenaline etc)
Because the phenylalanine isn’t being converted into tyrosine, the transport protein moving it into the brain becomes saturated and there is an increased level of it in the blood. As a result little or no phenylalanine gets into the brain
The circulating phenylalanine is converted into phenylpyruvate instead
How do you treat PKU?
Decrease protein intake in diet
Will a patient with PKU requires a dietary source of tyrosine? Explain
Yes because it becomes an essential amino acid for that individual
How is homocystinuria similar to marfan syndrome? How is it different?
Both have symptoms of: Lens dislocation
Skeletal deformation
Risk of cvs complications/diseases
Difference: homocystinuria sufferers will have neurological issues
