April 1, 1910] 



SCIENCE 



505 



by Traube as oxidizing ferments, form com- 

 pounds of the nature of peroxides which pro- 

 mote and accelerate the oxidation of other 

 substances. This view may be represented 

 in its simplest form by the two following 

 equations in which A constitutes the oxidizing 

 ferment and B the substance whose oxidation 

 is effected through the agency of this ferment : 

 A-l-02 = A0j 

 AO:-f B=AOH-BO 



The third period considered by the author 

 extends to the present time and begins with 

 the work of Toshida, Bertrand and others 

 upon specific oxidases, particularly upon lac- 

 case and tyrosinase. The very interesting 

 literature upon these and related oxidases is 

 reviewed at length, and the author suggests 

 the following classification of the oxidases as 

 being in accord with our present knowledge: 



1. Laccase; ferments oxidizing guaiacum, 

 guaiacol, hydroquinone, phenolphthalin, tan- 

 nin, etc., directly by means of atmospheric or 

 dissolved oxygen, and without the interven- 

 tion of hydrogen peroxide. 



2. Tyrosinase; ferments acting on tyrosin 

 and related substances, and responsible pos- 

 sibly for the production of melanin and other 

 pigments in plants and animals. 



3. Aldehydases; ferments oxidizing aro- 

 matic aldehydes and related compounds. 



4. Indophenol oxidase; ferments oxidizing 

 a mixture of a-naphthol and para-phenylene 

 diamine to indophenol. 



5. The purin oxidases. 



6. The glycolytic ferments, causing the dis- 

 appearance of sugar from animal tissues. 



Closely related to these oxidases are the 

 following catalytic agents which act in con- 

 junction with hydrogen peroxide or related 

 organic peroxides : 



1. Peroxidases; ferments which exert an 

 oxidizing reaction only in the presence of a 

 peroxide, such as hydrogen peroxide. 



2. Catalases; ferments which actively de- 

 compose hydrogen peroxide. 



3. Oxygen carriers (not true ferments) ; 

 this class includes substances such as hemo- 

 globin and hemocyanin which are capable of 

 activating the oxygen of hydrogen peroxide, 



even after their solutions have been heated 

 to 100° C. 



This classification brings up the perplexing 

 question of the distinction made between the 

 oxidases and peroxidases. According to the 

 well-known views of Bach and Chodat aU 

 oxygen-activating ferments are really perox- 

 idases. So-called oxidases, such as laccase and 

 tyrosinase, consist of certain substances (oxy- 

 genases) capable of forming with oxygen 

 unstable compounds of the nature of perox- 

 ides. The oxygen in these peroxides is ren- 

 dered active by the ferment bodies designated 

 as peroxidases. Laccase differs from tyro- 

 sinase in the specific nature of the constituent 

 peroxidase. Kastle evidently does not hold to 

 this or similar views, but recognizes the exist- 

 ence of at least two classes of oxidizing fer- 

 ments, the oxidases and the peroxidases, as 

 defined in the classification given above. As 

 far as the peroxidases are concerned, he con- 

 ceives that they are substances which are 

 capable of producing peroxides either by 

 double decomposition with hydrogen peroxide, 

 or by forming an unstable addition product 

 with hydrogen peroxide. These two possible 

 reactions and the resulting activation of the 

 oxygen are indicated schematically in the fol- 

 lowing equations in which P represents a 

 peroxidase : 

 (1) P + HA = PO, -f-H,0 



PO: + B = BO + PO, or 



POj -f 2B = P + 2B0 



(2) 



P-1-H,02 = H,P0, 



HjPOj -I- B = P -I- BO + H,0 



Kastle emphasizes the fact that the perox- 

 idase reaction, as also the catalase reaction, 

 constitutes one of the most universal and per- 

 sistent properties of living tissues. When 

 these reactions fail there can be no question 

 that the tissue or organism concerned is dead. 



In other sections of the review the author 

 treats of the oxygen catalysts of blood in 

 health and disease; of the very interesting 

 discoveries in regard to the part taken by cer- 

 tain metals such as manganese, copper and 

 iron in the activity of the oxidases and the 

 peroxidases, and of the suggestive work done 



