408 



IX. HEMATIN ENZYMES, II 



of heme with seven or eight groups; there is in fact no evidence that 

 hydrogen peroxide is bound in the ferrous azide compound, nor is 

 there any need to assume a Hnkage to peroxide or azide in the carbon 



X 



Azide catalase 



/ >••/.....••••■ Catalase (pH 6.8) 

 / fl ^ Azide catalase + H2O2 in N2 

 .^Azide catalase + H2O2 in CO 



480 



WAVELENGTH, m/x 



Fig. 1. Absorption spectra of catalase and its derivatives determined with the 

 Hilger-Nutting spectrophotometer (after Keilin and Hartree, i^99). /3 = (l/cZ) In (/o//), 

 where c = concentration of catalase in gram moles hematin per milliliter, / = depth 

 of liquid layer in centimeters, and 7o and / = intensities of incident and transmitted 

 light, respectively. 



monoxide compoimd, since carbon monoxide may replace azide. The 

 main point is that hydrogen peroxide in some way reduces azide 

 catalase to a ferrous compound, which dithionite is unable to do. 

 This will be discussed further in Section 4. 



^The magnetochemical results of Theorell and Agner (2780) indi- 

 cated the presence of one free electron in the red azide compound 

 produced by hydrogen peroxide. Keilin and Hartree (1499) have 

 pointed out, however,' that the instability of the compound renders 

 the magnetochemical studies inconclusive. The magnetic suscepti- 

 bility can be explained by assuming that during preparation for 



