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PHENYLKETONURIA (PKU)

PHENYLKETONURIA (PKU). (a). (b). The normal metabolism of phenylalanine (pathways a and b ). BREAKDOWN. Dietry sources, particularly plant proteins. PHENYLALANINE HYDROXYLASE. PHENYLALANINE. TYROSINE. BODY PROTEINS. © 2008 Paul Billiet ODWS. (c).

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PHENYLKETONURIA (PKU)

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  1. PHENYLKETONURIA (PKU)

  2. (a) (b) The normal metabolism of phenylalanine (pathways a and b) BREAKDOWN Dietry sources, particularly plant proteins PHENYLALANINEHYDROXYLASE PHENYLALANINE TYROSINE BODY PROTEINS © 2008 Paul Billiet ODWS

  3. (c) Dietry sources, particularly plant proteins PHENYLALANINEHYDROXYLASE PHENYLALANINE* (a) (c) (b) BODY PROTEINS HYDROXYPHENYLACETIC ACID The abnormal metabolism in phenylketonuric subjects (pathway c) PHENYLACETIC ACID* *Agents, thought to be responsible for mental retardation © 2008 Paul Billiet ODWS

  4. Test • Ferric chloride + urine of new born baby Green colour in the presence of ketone bodies © 2008 Paul Billiet ODWS

  5. Treatment • A strictly controlled phenylalanine free diet • up to the age of about 14 years old • phenylalanine is itself an essential amino acid small doses must be supplied • After this age the growth and development of the brain is not affected by high levels of phenylalanine in the body © 2008 Paul Billiet ODWS

  6. Frequency • 1 in 10 000 in Caucasians of NW Europe © 2008 Paul Billiet ODWS

  7. Causes • A single mutant recessive allele of the Phenylalanine Hydroxylase (PAH) gene Locus : Long arm of Chromosome 12 • Dietary excess of plant proteins which results in the exhaustion of a protein cofactor (pterin) needed by the enzyme © 2008 Paul Billiet ODWS

  8. Evolution • Heterozygotes (carriers) are thought to be less susceptible to toxins produced by the moulds Aspergillus and Penecillium • These grow on foods in damp wet climates (e.g. NW Europe) • Heterozygous women show lower spontaneous abortion rates © 2008 Paul Billiet ODWS

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