406 IX. HEMATIN ENZYMES, II 



the following pK values were found: phosphate 4.83, acetate 6.27, 

 fluoride 7.66, formate 9.15. In the absence of anions (FeOH) is 

 half-dissociated at pH 3.8. 



Catalase cannot be reduced by dithionite, the absorption spectrum 

 remaining unaltered. After denaturation of the protein by alkali 

 the spectrum becomes that of a hem/chrome (575, 545 m/x) and 

 dithionite now reduces it to a protohemochrome. The bands of this 

 are not altered by pyridine. x\ccording to Zeile and co-workers {316Jt) 

 catalase can be reduced by dithionite after treatment with hydrogen 

 sulfide or in the presence of washed liver slices; Keilin {14-99) could 

 not confirm this observation. Recently Dounce and Rowland (615) 

 observed that crystalline ox liver catalase after being dried in the 

 frozen state can be reduced by dithionite to a compound with two 

 absorption bands (594, 560 mpt). This absorption spectrum resembles 

 that of reduced peroxidase. This catalase preparation was, however, 

 largely inactive. 



TABLE I 



Spectroscopic and Magnetochemical Data on Compounds of Catalase 



" In the spectrophotometer the absorption spectrum shows only an inflection at 



580 mix. 

 ^ Band higher than that of uncombined catalase. 

 ' If hydrogen peroxide is added more slowly. 

 ^ Somewhat higher than would correspond to one unpaired electron. 



Table I gives the absorption spectra of vaVious compounds of 

 catalase together with the numbers of unpaired electrons found by 

 Theorell and Agner {2780) by magnetochemical investigation of 



