Evidence supports the theory that an unknown disease causing mental retardation surfaced among wives and slaves of Vikings in Ireland and Scotland long ago. Despite this Celtic origin, it was not until 1934 that a biochemist named A. Folling from Norway discovered phenylketonuria through urine testing. He correctly identified the disease as one in which the body cannot handle phenylalanine, an essential amino acid found in protein. Then in 1947, George Jervis, an American scientist presented that the exact cause of PKU was an enzyme found in the liver called phenylalanine hydroxylase (PAH). Discovery of a mutant PAH enzyme made it possible to start searching for treatments for the condition. It is now commonly accepted that Phenylketonuria, often called PKU for short, is an inborn error of protein metabolism. In other words, the body is unable to produce proteins or enzymes needed to convert certain toxic chemicals into nontoxic products. The inability of the body to complete this process can lead to neurological damage. Phenylketonuria involves one particular part of a protein, the amino acid called phenylalanine, or PHE for short. When an individual eats food-containing protein, various enzymes break down the protein into amino acids used for the body’s growth and repair of its tissues. Everyone needs a certain amount of PHE to perform these functions. Most of the time the unused PHE is then converted to another amino acid. In the case of PKU, the disorder is inherited when a baby inherits two mutant genes for the enzyme phenylalanine hydroxylase. A mutant gene for PKU occurs as a result of a mutation at the PAH locus, 12q24 which is considered to be a large gene being 90 kb long with 13 exons and encoding a polypeptide of 452 amino acids. There are over 365 identified possible mutant alleles that play a role in PKU and 105 of the mutations are found on the gene encoding for PAH. Most PAH variants are single-base ...
