260 SCIENCE PROGRESS 



Bach and Chodat x came to the conclusion that two classes of 

 oxidising enzymes exist, namely, oxygenases, or enzymes which 

 take up molecular oxygen and become converted into peroxides 

 or transfer it to other suitable organic substances with peroxide 

 formation, and peroxidases, or activators which assist in the 

 transference of this active peroxide oxygen to oxidisable sub- 

 stances. Hence oxygenases are directly comparable to H 2 2 , 

 and peroxidases to activators such as FeS0 4 . The existence of 

 these two classes of enzymes, both in plants and animals, is 

 generally accepted, though the evidence concerning animal 

 peroxidases is rather contradictory. Almost all animal tissues, 

 unless very thoroughly washed, contain haemoglobin, and this 

 substance can function as an activator just like other iron salts ; 

 but its activity is not much affected by heating, whilst that of 

 true peroxidases is destroyed at about 6o° C. Peroxidases are 

 usually tested for the addition of H 2 2 and guiaconic acid, 

 which leads to the production of guiacum blue, but the test is 

 not a safe one. Hydriodic acid is oxidised by peroxidases to 

 free iodine in presence of H 2 2 , but this test is likewise uncertain 

 in its action. 2 Battelli and Stern 3 found that in presence of ethyl 

 hydrogen peroxide — which is preferable to hydrogen peroxide — 

 peroxidases oxidise formic acid to C0 2 4- H 2 0, and the volume 

 of C0 2 evolved affords a rough quantitative measure of the 

 peroxidase present in a tissue. Liver proved most active of 

 all, whilst blood came next and oxidised about half as much 

 formic acid as liver, though it contained only the " pseudo- 

 peroxidase " haemoglobin. Kidney, lung, and spleen were 

 about half as active as blood, whilst muscle and brain were 

 only a quarter as active. 



For testing the direct oxidases or oxygenases of the tissues 

 a number of different colour reactions have been employed, but 

 for the most part they have been used only qualitatively. As 

 a quantitative method one of the best reactions appears to be 

 the indophenol test, first used by Rohmann and Spitzer 4 in 

 1895. If solutions of a-naphthol and ^-phenylenediamine be 

 mixed in presence of sodium carbonate, oxygen is absorbed 

 from the air and the purple indophenol is gradually produced, 



1 Bach and Chodat, Biochem. Centralb. 1, p. 417, 1903. 



' V. Czyhlarz and v. Fiirth, Beitr. z. chem. Physiol, u. Path. 10, p. 358, 1907. 



3 Battelli and Stern, Biochem. Zeit. 13, p. 44, 1908. 



4 Rohmann and Spitzer, Ber. 38, p. 567, 1895. 



