Phenylketonuria Lab Quest

1. What enzyme is most commonly defective in people with phenylketonuria?

The enzyme that is most commonly defective in people with phenylketonuria is chromosome 12. This gene is known as PAH and is produced in the liver to help convert amino acids into another amino acid known as tyrosine. People with phenylketonuria have a mutated PAH gene that creates a mutated PAH enzyme.

2. What reaction does this enzyme catalyze? (What is the substrate and what product is produced?)

The substance in the amino acid, phenylalanine. The PAH enzyme turns the phenylalanine amino acid into another amino acid called tyrosine. The way it does this is, the PAH enzyme grabs and oxygen atom and attaches it to the bottom of the phenylalanine. Then a hydrogen attaches itself to the bottom of the oxygen atom, creating tyrosine. Since there are many different mutations of the PAH gene. There are also many things that can go wrong with this mutated gene. The mutation changes the shape of the PAH gene and in one gene the shape is changed and the PAH enzyme cannot recognize the phenylalanine. Sometimes the PAH gene is changed to where it works extremely slow. No matter what is wrong with the phenylalanine, it will not turn into tyrosine.

3. Describe the symptoms of phenylketonuria.

There are many different symptoms of phenylketonuria. Some symptoms are a child may be born with a smaller head than normal, epilepsy, and mental retardation. Sometimes the extra phenylketonuria in skin creates a musty odor. Also the child may be born with lighter skin and a lighter color of hair.

4. What causes the symptoms of PKU, the lack of a substance or the buildup of one? Explain.

The causes of the symptoms of PKU is due to, to much phenylalanine which is the cause of mental retardation and causes problems in the brain that deal with communication. Also its important to know that the appearnce changes are caused by a lack of tryosine.

5. How common is phenylketonuria? How is it treated?

PKU is very rare. Around 1 out of every 15,000 infants born have PKU. If you do have it, you can treat it. PKU is very treatable. People that happen to have PKU eat a low protein diet.


For more information PKU, click on the links below.

http://willroberts.com/pku/

Newborn Screening in Colorado

http://www.nspku.org

http://www.ygyh.org