Enzymatic Ability

• Amazingly, one catalase molecule is able to convert millions of hydrogen peroxide molecules into gaseous oxygen and water in a single second. Four reactive sites each hold an iron ion that speeds the reaction.
  
  

Role as an Antioxidant

• Catalase functions as an antioxidant. It breaks down hydrogen peroxide, itself a product of the breakdown of another free radical, superoxide. The antioxidant enzyme superoxide dismutase creates the hydrogen peroxide from superoxide; catalase takes over from there.
  
  Free radicals can cause a destructive chain reaction that inhibits the function of many molecules. With an unpaired electron, free radicals can scoop up an electron elsewhere, causing the now-deficient molecule to borrow an electron from elsewhere, and so on down a chain of atoms and molecules.
  
  For example, iron can break hydrogen peroxide into hydroxyl radicals that mutate DNA.
  
  

Breakdown Process

• Catalase breaks down hydrogen peroxide in two steps. A hydrogen peroxide molecule is broken apart, with an iron ion in the catalase latching onto an oxygen molecule. The rest of the hydrogen peroxide molecule (H2O2) is set free as water (H2O). Then another hydrogen peroxide molecule is broken apart, with the same iron ion breaking off an oxygen atom, to be combined with the first detached oxygen atom, to be released as oxygen gas (O2).
  
  

The Catalase Test

• Catalase is used in the lab for various reasons. A common test to differentiate bacteria is to apply hydrogen peroxide to see if oxygen bubbles form. If so, the bacteria are of a class that produces catalase.
  
  

Prospective Use

• Catalase breaks down the hydrogen peroxide naturally produced by the body. Studies have found that reduction in catalase production is correlated with gray hair, suggesting that high hydrogen peroxide levels are behind gray hair. This suggests a possible cure, either applying catalase directly or returning its production to previous levels.