PHENYLKETONURIA (PKU)
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
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
Test Ferric chloride + urine of new born baby Green colour in the presence of ketone bodies © 2008 Paul Billiet ODWSODWS
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
Frequency 1 in in Caucasians of NW Europe © 2008 Paul Billiet ODWSODWS
Causes 1. A single mutant recessive allele of the Phenylalanine Hydroxylase (PAH) gene Locus : Long arm of Chromosome Dietary excess of plant proteins which results in the exhaustion of a protein cofactor (pterin) needed by the enzyme © 2008 Paul Billiet ODWSODWS
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