peroxidase

Peroxidase is any of a group of enzymes which remove hydrogen peroxide (H₂O₂) from a cell by turning it into water and oxygen.

Hydrogen peroxide is a very harmful radical that, if left to its own molecular devices, will cause extensive damage to DNA. These enzymes are thus very important to all living things which use oxygen (aerobes) because the use of oxygen in respiration often results in the formation of hydrogen peroxide as a waste product. The formation of hydrogen peroxide is also a major reason why obligate anaerobes find oxygen to be a poison.

Here are a few peroxidases:

• catalase is type of peroxidase which is mostly found in small organelles called peroxisomes, which are found in the cytoplasm of a cell.
  
  
• glutathione peroxidase is an enzyme that begins the oxidation of glutathione (a peptide important in a variety of tissue processes) by hydrogen peroxide. Selenium is an important component of this enzyme.
  
  
• horseradish peroxidase (HRP) is the version of the peroxidase enzyme isolated from the horseradish plant. It is used to label proteins and nucleic acids as an alternative to radioactive labelling. The molecule to be labeled is attached to the HRP molecule, and the mixture is then exposed to a substrate that changes from clear to colored when it is oxidized by HRP.

From the BioTech Dictionary at http://biotech.icmb.utexas.edu/. For further information see the BioTech homenode.