Re: why does the concentration of catalase vary in different liver tissues?

Let me first mention that I'm impressed you're doing a catalase assay in 
high school.    

Catalase is a bifunctional enzyme that resides in peroxisomes.  It can 
oxidize substrates such as ethanol by using hydrogen peroxide as an oxidant 
(the peroxidase reaction), and it also breaks down hydrogen peroxide into 
water and oxygen gas (the catalase reaction).  Hydrogen peroxide destroys 
DNA and proteins, so eliminating it from the cell is important.  Catalases 
are found in all organisms (including bacteria) that live in aerobic 
(oxygen-containing) environments.  

My guess is that liver has a higher level of catalase than the kidneys 
because it has to handle more detoxification reactions than do the kidneys.  
As a result, catalase production is greater in the liver in comparison to 
catalase production in the kidney.  In other words, a higher level of a 
catalase substrate in the cell should lead to higher levels of catalase.  

I do not know why catalase levels would differ from species to species, 
other than that chickens and cows have different diets which would require 
different levels of catalase.  Plus, they're distantly related organisms 
that have distinct physiological differences.  

If you need more information, please write back.

Sarah Earley
CU Boulder