Similar term(s): Phenylketonuria, homozygote for PKU, heterozygote for PKU.
A hereditary genetic disease involving liver enzyme deficiency.
A person with PKU is completely or nearly completely deficient of the enzyme
phenylalanine hydroxylase found in the liver. This enzyme is able to convert the
essential amino acid phenylalanine to another amino acid called tyrosine.
Without this enzyme (phenylalanine hydroxylase), the conversion cannot take
place and if action is not taken to control the intake of phenylalanine, it will
accumulate in the blood and body tissues. This is a concern as chronic high
levels of phenylalanine and some of its breakdown products can have effects on
As an essential amino acid, phenylalanine can only be obtained from protein in
the food we eat. People with PKU can limit the intake of phenylalanine by
limiting the amount of high protein foods they eat. They thus avoid eating meat,
fish, poultry, eggs, cheese, milk, dried beans and peas.
As some phenylalanine is required for normal growth, a diet is required where
some phenylalanine is present but in much lower amounts than normal.
Phenylalanine free formulas are available but a controlled diet can be followed
where cereals, starches, fruits, and vegetables are eaten and a milk substitute
Phenylketonuria (PKU) is a hereditary disease, that is, to have it you need to
inherit it from your biological parents. People who inherit PKU from both
parents are homozygote for PKU and display all the symptoms listed above.
Approximately, 1 individual in 10,000 is homozygote for PKU.
People who inherit PKU from only one parent are heterozygote for PKU, and are
carriers for PKU. Carriers do not have symptoms of the disorder, they are
healthy but can pass the gene on to their children.
Chronic - Enzyme(s) - Heterozygous for PKU - Homozygous for PKU - Phenylalanine - Tissue
To read about this term in context:
GreenFacts Summary on Aspartame:
Français: PCU (Phénylcétonurie)