BIOLOGICAL FUNCTION OF CATALASE 



415 



against 0.1 iV hydrochloric acid. Several authors {2699 ,27 1^ If) have, 

 however, been unable to confirm this observation. Evidently it is 

 impossible to renature the denatured protein. 



TABLE III 



Fractions of Catalase Hydrolyzate" 



" According to Theorell and Akesson (2786). 



2.7. Biological Function of Catalase 



2.7.1. Occurrence of Catalase. Catalase is ubiquitous in aerobic 

 cells and is lacking only in strict anaerobes and in a few facultative 

 anaerobes. In general, the organisms possessing a cytochrome system 

 also contain catalase; (the converse is also true). An exception is 

 Acetohacter yeroxydans which shows cytochrome bands, but does not 

 contain catalase. It is likely that its cytochrome bands are due to the 

 presence of a peroxidase which protects the organism against hydrogen 

 peroxide (3073). Shigella dysenteriae has also been reported to con- 

 tain no catalase. In yeast cytochrome and catalase contents have 

 been found to vary in parallel {708). 



While catalase is ubiquitous in aerobic cells, it is highly concen- 

 trated in a few animal tissues (liver, red cells). Assuming a Kat.f. of 

 60,000 for pure catalase, the concentration in horse liver is about 

 0.03% and in blood, 0.05%, i.e., 10 ""^ to l^Hl {2697). These are 

 minimal values which neglect the presence of inhibitors in the tissues. 

 In all other tissues the concentration of the enzyme is far smaller. 

 Liver cell nuclei do not contain catalase {613). 



