ISOLATION OF CATALASE 403 



different substrate. Second, peroxidative activity depends more markedly on 

 pH than does catalatic activity (lOU) and again the pH optimum varies 

 with the substrate. It may also vary with the solvent. Haurowitz (1168) 

 gives the following values, in moles of hydrogen peroxide used per mole of 

 hematin per hour: with iodide (pK 5.7), 2; with pyrogallol in aqueous solution 

 of pH 6.8, 15; with pyrogallol in acetic acid or in methanol, 1000; with 

 benzidine in 20% acetic acid, 11,000. This illustrates both points. 



In the studies on peroxidative activity of hematin compounds a variety of 

 substrates have been used, such as pyrogallol, which is oxidized to purpuro- 

 gallin il29,16U,3090), phenolphthalin and other leuco dyes {717,723,7U), 

 benzidine (2332), hydriodic acid {328,16UJ615), and ascorbic acid {897JUL 

 2163). For the peroxidative oxidation of hydrogen sulfide, inorganic iron is 

 a better catalyst than hematin, while horse-radish peroxidase is entirely 

 inactive (2965,2966). Of the substrates mentioned, only pyrogallol (as a 

 polyphenol) and possibly ascorbic acid are of biological interest. 



With benzidine as substrate, protohematin and other hematins closely 

 related to it are stronger peroxidases than hematins derived from chlorophyll 

 porphyrins (2232). 



With pyrogallol as substrate, hemochromes are only slightly, hemoglobin 

 derivatives ten to twenty times, more active peroxidases than hematin (129). 

 Bancroft and Elliot give the following values for the purpurogallin number 

 (PZ) (cf. Section 3.2.4.) per mg. iron: hematin 1.6, pyridine-hemichrome 

 4.5, hemoglobin 16, denatured globin hem/chrome 35. Compared with horse- 

 radish peroxidase activity, which in these units would be of the order of 10', 

 all these values are very small. With iodide as substrate, similar observations 

 were made by Kuhn and Brann (1614J615). Imidazole hem?chromes were 

 found to be about twice as active as other hem/chromes (16JfJ^). The peroxi- 

 dative activity of hemoglobin was first shown by Moitessier (1968) and 

 studied by Bach (110); carbon monoxide does not inhibit the reaction. 

 Jayle (llt.ll)* found hemoglobin at pH 4-5.5 a strong peroxidase with ascorbic 

 acid as substrate, while at pH 7.2, in contrast to Fischer (897), he found little 

 activity. The studies of Polonovski on the peroxidative action of hemoglobin 

 are of some interest with regard to the mechanism of peroxidase action and 

 will be discussed in this connection. 



2. CATALASE 

 2.1. Isolation 



Catalase is best prepared from the mammalian liver or from 

 erythrocytes, both of which contain the enzyme in comparatively 

 high concentrations. The preparation from erythrocytes is more 

 difficult, since it requires separation of the enzyme from a large excess 

 of hemoglobin, but leads to preparations of greater purity and higher 

 activity. 



* More recent publications of this author (Hlla) have not been available. 



