1. PHENYLKETONURIA (PKU)

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

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

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

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 ODWSODWS

6. Frequency  1 in 10 000 in Caucasians of NW Europe © 2008 Paul Billiet ODWSODWS

7. Causes 1. A single mutant recessive allele of the Phenylalanine Hydroxylase (PAH) gene Locus : Long arm of Chromosome 12 2. Dietary excess of plant proteins which results in the exhaustion of a protein cofactor (pterin) needed by the enzyme © 2008 Paul Billiet ODWSODWS

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 ODWSODWS