30 



mixture was observed. In this regard, therefore, that oxidase would 

 resemble laccase more thau it would tyrosinase.^ 



To extract oxidases from fermented or cured tobacco as completely 

 as possible it is necessary to thoroughly pulverize the samples and to 

 let the water act for some time at from 20^ to 30^ 0. (68o to 86° F.) 

 before filtering. After complete drying, the samples can be easily pul- 

 verized- very fine. The following experiment proves that when the tis- 

 sue is not pulverized the peroxidase is but very imperfectly extracted, 

 the passage through the cellular walls being quite slow. Fermented 

 tobacco leaves were three times soaked in water and the brown liquid 

 pressed out, the first soaking lasting half an hour and the second and 

 third soakings five minutes each. Altliouglj the sample was thus nearly 

 exhausted, it nevertheless yielded, when left with some alcohol of 30 

 per cent for one day, a light-colored liquid with a very intense reaction 

 for peroxidase. 



It may safely be' assumed that in the majority of instances the oxi- 

 dase will prove the more energetic of the two oxidizing enzyms. For 

 example, its action upon i)yrocatequol and hydroquinone is much more 

 energetic than that of the peroxidase. On the other hand, however, 

 the former succumbs much more quickly to noxious influences, e. g., the 

 action of alcohol or rising temperature. 



The fact that the peroxidase forms guaiac blue from guaiaconic acid 

 with the aid of hydrogen i)eroxide only does not indicate that its oxi- 

 dizing action in every case depends upon the presence of the latter. ^ 

 The peroxidase can, on the contrary, also exert oxidizing action upon 

 various compounds without the assistance of hydrogen i)eroxide. Thus, 

 para-amido]3henol is gradually changed by it to a dark brown sub- 

 stance. 



Hydroquinone in dilute solution gradually assumes a reddish color in 

 the presence of the i)eroxidase, but in its absence there is scarcely a 

 trace of coloration within twenty-four hours. 



Fyrocatechol is scarcely attacked by the peroxidase within twenty- 

 four hours, but on a further addition of a little hydrogen peroxide it 

 turns to a dark brown in five minutes. Hydrogen peroxide added alone 

 does not act thus. 



Pyrogallol is slowly attacked by the peroxidase and turns brown in 

 twenty-four hours. The oxidase acts also in this case much more ener- 

 getically than the peroxidase. 



Tannin solution shows in twenty-four hours a yellow color in the 

 presence of the peroxidase, but in the control solution merely a slight 



1 The peroxidase of tobacco on tlie otlierhand bears resemblance to tbe peroxidase 

 of pus described by Linossier. 



"The hydrogen peroxide is decomposed by enzyms into water and oxygen, but 

 this oxygen in status nascens is charged with more chemical energy than the free 

 oxygen of the air, i. e., the two atoms constituting the molecule are For a time in 

 a more energetic motion than in the latter case, hence the action of the oxidizing 

 enzyms is facilitated by this nascent oxygen. 



