The EPX gene provides instructions for making a protein called eosinophil peroxidase. This protein is found within certain white blood cells called eosinophils. During a normal immune response, eosinophils are activated (turned on), and they travel to the area of injury or inflammation. The cells then release proteins and other compounds that have a toxic effect on severely damaged cells or invading organisms. One of these proteins is called eosinophil peroxidase. This protein helps form molecules that are highly toxic to bacteria and parasites. These toxic molecules also play a role in regulating inflammation by fighting microbial invaders.
The eosinophil peroxidase protein is produced as a long strand that is cut (cleaved) into two smaller pieces. The shorter piece is known as the light chain and the longer piece is known as the heavy chain. These two pieces are attached to each other to form functional eosinophil peroxidase.
At least three mutations have been found to cause eosinophil peroxidase deficiency. This condition affects eosinophils but causes no health problems in affected individuals. These mutations reduce or prevent eosinophil peroxidase production or result in a protein that is unstable and nonfunctional. As a result, eosinophils have severely reduced amounts of eosinophil peroxidase or none at all. The cells lacking eosinophil peroxidase are smaller and may have structural changes, but the other proteins within affected eosinophils are normal and the loss of eosinophil peroxidase does not appear to impair the function of these cells.
- eosinophil peroxidase preproprotein