Phenylketonuria (PKU)

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Phenylketonuria (PKU)
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PKU at a Glance

• Name of disorder Phenylketonuria (PKU)
• OMIM number 261600
• inheritance pattern autosomal recessive

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PKU At A Glance

• PKU is a metabolic disorder caused by a
  deficiency of the liver enzyme phenylalanine
  hydroxylase. It prevents normal metabolization of

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PKU At A Glance

• phenylalanine (Phe), one of the essential amino
  acids that cannot be manufactured by the body
  and must therefore be consumed in protein rich
  foods.

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PKU At A Glance

• Untreated individuals may give off a musty odor
  and they excrete large amounts of phenylalanine
  in their urine.

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Phe to Tyr Conversion

• Enzymes are structures that allow amino acids to
  combine by acting on a substrate and producing a
  new product. Individuals with PKU have a
  deficiency in the enzyme

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Phe to Tyr Conversion

• phenylalanine hydroxylase, which converts
  phenylalanine to tyrosine.

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Phe to Tyr Conversion
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Metabolic Pathways

• In individuals with PKU, phenylalanine cant be
  converted into tyrosine, and the metabolic
  process stops short of producing the needed end
  products.

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Metabolic Pathways

• Phenylalanine builds up in the body to toxic
  levels, causing mental retardation.

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PKU Genetics

• The PKU gene is found on the q arm of chromosome
  12, locus 24.1 in the phenylalanine hydroxylase
  gene

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PKU Genetics
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PKU Onset

• The inability to metabolize PKU exists from the
  time the infant is in the womb.
• Infants are screened for PKU by a blood test
  shortly after birth.

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PKU Onset

• High levels of phenylalanine in the blood
  indicate an inability to process the amino acid,
  and thus indicate that an individual is affected
  by the disorder.

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PKU Onset

• Testing must be accomplished quickly since the
  inability to process phenylalanine means it can
  build up to toxic levels and cause severe mental
  retardation.

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PKU Treatment

• The only treatment available for PKU is a diet
  where phenylalanine levels are strictly limited.

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PKU Treatment

• Meat, fish, eggs, cheese, milk products, legumes,
  and bread are all foods that have high levels of
  phenylalanine

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PKU Treatment

• Artificial protein substitutes are given which
  contain amino acids without phenylalanine

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PKU Prognosis

• If the condition was not diagnosed early and a
  special diet started, the indidivudal will suffer
  severe and irreversable brain damage.

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PKU Prognosis

• If detected early, the individual will develop
  normally but will have to follow the special diet
  at least until adolescence, if not throughout
  their entire life.

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PKU Prognosis

• Women with PKU who wish to become pregnant must
  also eat the special diet, since children in the
  womb affected with PKU will not be able to
  metabolize the phenylalanine the mother ingests.