What Is PKU

PKU is the abbreviation for Phenylketonuria. PKU is a metabolic disturbance, which was proven in 1934 by the Norwegian physician Dr. A. Folling. The strange smell of the urine of their two mentally handicapped children had been noticeable to a mother. Dr. Folling succeeded the proof of one normally in the urine not contained Metabolism product, which because of its chemical condition was called " Phenylketon " (from which also the name PKU is then derived).

PKU is a pass down disturbance in the Phenylalanine Metabolism.



Phenylalanine is a constituent of protein (amino acid)

Phenylalanine belongs to the 8 essential (vitally necessary) amino acids

In our bodies, Phenylalaninine is changed into Tyrosine (A different Amino Acid) by an enzyme called Phenylalanine Hydroxylase.

Tyrosine is an amino acid used in the body to make certain Hormones, Pigments (mainly Melanin) and catecholamines.


And what is disturbed?

In PKU, the activity of the enzyme Phenylalanine Hydroxylase is completely (or partly, a much rarer condition) missing. This is due to a genetic defect in which the DNA code sequence that tells cells to make Phenylalanine Hydroxylase is missing. This means that people who suffer from PKU usually cannot produce the Phenylalanine Hydroxylase.

* The Phenylalanine that has not been converted into Tyrosine collects in the blood, and gradually "floods" the body.
* Because Tyrosine is not being produced properly, the protiens which require Tyrosine cannot be made properly.
* The excess Phenylalanine is excreted in other ways of the metabolism, also the "Phenylketone" forms, which gives the name to the condition.
* Excess amounts of Phenylalanine in th brain of a child can cause brain defects. It is not known exactly why as of yet.

How is it passed down?

PKU is inherited from parents. The defective gene that causes it is known as a "Recessive Allele". This means that a person must inherit PKU from both parents to fully suffer from it. "Carriers" of PKU are not affected by the disease.

PKU Inheritance

  Inheritance of the PKU gene. Taken from http://en.wikipedia.org/wiki/Image:Autorecessive-3.png