384 RESPIRATORY METABOLISM 



function of these essential compounds is known or indicated, they seem 

 to be necessary for the formation or at least for the normal functioning 

 of the respiratory enzymes (review, A. Lwoff, 1938). Recent work on 

 the supposed function of most of these substances has been reviewed by 

 Burk (1937) and Stern (1938). 



6. THE DETECTION OF OXIDASE, PEROXIDASE, AND CATALASE 



No extensive investigation of isolated enzyme systems of the Protozoa 

 has been made. Certain enzymes, especially oxidase and peroxidase, are 

 supposed to react with certain stains so that the position of the enzyme 

 may be located in the cell. The methods used involve the Nadi, 

 Dopa, benzidine-HoOo, and pyronine-anapthol-HoO, reactions (methods 

 given by Roskin and Levinsohn, 1926; Guyer, 1936; McClung, 1937). 

 These reactions are important in studying vertebrate blood and nerve 

 cells, but apparently no correlation has been made of the presence of 

 "oxidase" or "peroxidase" granules, detectable by these methods, and 

 the respiratory mechanisms discussed above, and it has not been demon- 

 strated that these reactions are specific for oxidase or peroxidase. Several 

 observations have been made on the Protozoa (Roskin and Levinsohn, 

 1926; Bles, 1929), and when more is known about the respiratory 

 mechanisms of the Protozoa it might be possible to correlate the results 

 of staining and of manometric methods. However, such attempts are 

 omitted in the present discussion. Perhaps a certain degree of localization 

 of the enzymes could be obtained by centrif uging the organisms and mak- 

 ing activity tests on cell fragments, as has been done for peptidase in 

 marine ova (Holter, 1936). 



The presence of catalase can be detected by adding hydrogen peroxide 

 to a cell suspension and measuring (chemically or manometrically) the 

 oxygen evolved. Burge (1924) studied the catalase action of 'Paramecium 

 and Colpoda and found that it was decreased by ether and chloroform, 

 but not by ethylene or nitrous oxide. A much more accurate method was 

 used by Holter and Doyle (1938), who found that the average catalase 

 activity per individual of Frontonia, Varamec'mm, and Amoeba was in 

 the ratio 190:30:5. Considerable variation was found between different 

 cultures and even between different individuals from the same culture. 

 Reidmuller (1936) reported only a trace of catalase, no peroxidase, and 

 no indophenol oxidase for Trichomonas foetus. 



