Wednesday, December 8, 2010

Unpronouncable Words...And Lots of Them

As we've spent a large proportion of time recently discussing enzymes, I thought I'd put together a little post on a disorder of an enzyme: PKU. (I found most of this information in the Mayo Clinic article.)

Phenylketonuria (fen-ul-ke-toe-NU-re-uh) is a genetic defect that results in too much of the acid phenylalanine. It's caused by mutation within a gene that contains the instructions to make the enzyme that breaks it down. Amino acids are the fundamental building blocks of proteins, but too much of phenylalanine results in various health problems. People who have this excess of the phenylalanine, referred to as PKU, must carefully limit their diets so that they do not consume too much phenylalanine (which is found primarily in protein-rich foods).

At birth, babies within the U.S. and several other countries are screened for PKU. When it is caught soon after birth, serious complications can be prevented.
When a baby is born with PKU, he or she has no symptoms. Soon after, however, the various complications arise. These include:
  • Mental retardation
  • Behavioral or social problems
  • Seizures, tremors or jerking movements in the arms and legs)
  • Hyperactivity
  • Stunted growth
  • Skin rashes (eczema)
  • Small head size (microcephaly)
  • A musty odor in the child's breath, skin or urine, caused by too much phenylalanine in the body
  • Fair skin and blue eyes, because phenylalanine cannot transform into melanin — the pigment responsible for hair and skin tone
Let's go a little deeper with the causes of PKU:

PKU is caused by a genetic mutation. The gene that is defective is the one that carries the information used to make an enzyme that breaks down phenylalanine. Because this particular amino acid is allowed to flourish, a hazardous buildup of the acid can occur when a patient eats foods such as milk, cheese, nuts, or meats (foods that are rich in protein). This buildup leads to potentially serious health problems.

Because PKU is a genetic disease, the defective gene must be passed on to a child from both the mother and the father. This typically happens when the parents do not know that they have the defective gene. (Think of Typhoid Mary. People who have the defective gene but not PKU are known as carriers.)

Well, I think that's all for now! Who knows? I might actually stay on top of blog posts this time!

(Ha ha! How funny that is!) 

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