25 



The blackenin,:^'" of bananas some time after tbev are fratbered and the 

 brown color on the surfare of a sbce of apple may also be mentioned 

 as due to these agents. 



Oxidizing enzyms also occur in animal organisms, as the investiga- 

 tions of Fieri. Abelous, Bougault. Salkowski. Yamagiva, Linossier, 

 Jaquet. and Schmiedeberg have revealed. Sucli enzyms were found 

 in various organs, and are capable of easily oxidizing not only guaiac 

 tincture.' but also certain aldehydes, such as salicylic aldehyde. Spitzer 

 has determined the amount of oxygen liberated by difterent organs from 

 peroxide of hydrogen, and has observed that various poisons, such as 

 potassium cyanide, hydroxylamin, etc., small quantities of acids and 

 alkalies, and a temperature of about 70- C. (158- F.) destroy or 

 diminish the oxidizing action of this animal enzym. Water extracts 

 the enzym from the organs, and highly diluted acids, cautiously added, 

 precipitate it with all its original properties, f Abelous could, however, 

 IDrepare clear solutions only by api:)lication of potassium nitrate. ) It 

 has the character of a nucleo-proteid and contains from 0.19 to 0.23 per 

 cent of iron. On the other hand. Bertrand and Tilliers have found a 

 small amount of manganese in the vegetable oxidases. 



That oxidations also can proceed in certain cases without the aid of 

 oxidizing enzyms is a well-known fact. But this is only the case with 

 substances of a specific kind showing a great chemical energy, and 

 even in such cases the presence of oxidizing enzyms will cause such a 

 powerful increase of intensity that the difference becomes most striking, 

 especially when chromogens consisting of certain derivatives of poly- 

 valent phenols are present. The colored product (brown, red, or black) 

 formed by oxidation will api)ear much sooner and in much greater 

 quantity in the presence of certain oxidizing enzyms than in their 

 absence.- On the other hand, oxidizing enzynis can bring on oxida- 

 tions with certain compounds, as, for example, tyrosin, which under 

 ordinarj' circumstances would not be oxidized at all by the indifferent 

 oxygen of the air. 



Bertrand has characterized different oxidases. While the oxidase of 

 Rhus vernicifera. the Japanese lac tree, oxidizes mainly benzene deriva- 

 tives containing at least two hydroxyl or two amido groups in ortho or 

 para position, another oxidase, isolated trom certain green plants, as 

 well as from fungi, acts easily in tyrosin, which the former can not 

 affect, therefore he distinguishes the latter as tyrosinase from the 

 former as laccase. It is the laccase which acts upon the laccol in the 



1 This blue reactioD can be obtained not only by the action of oxidizing enzyms, 



but also by that of powerful oxidizing chemicals. Such bodies (nitrous acid, free 

 cblorme, etc.j are usually absent when the test for oxidizing enzyms is made. 

 Any intelligent chemist will be able to decide at once by control experiments 

 whether he can trare the reaction rapidly setting in to oxidases or not. 



-The attemjjt to explain such rapid oxidations by the assumption that certain salts 

 or ordinary albuminous matter would activify the oxygen, must be ctmsidered a 

 fadure. 



