72 ENZYMES 



of substances, one which activates the oxygen; the other the more 

 important class, which activates, by dissociation, the reducing sub- 

 stances. The latter are specific, the former not." This view has 

 received support by Bach. 



Peroxidase. — This name is given to an enzyme that is believed to 

 cause oxidation by activating peroxides, and is quite distinct from 

 catalase and from the other oxidases. The peroxide on which it chiefly 

 acts in the cell is supposed to be the so-called "oxygenase." 



Oxygenase. — This can also act as an oxidizer independent of the 

 peroxidase, in the presence of certain manganese compounds. Loeven- 

 hart and Kastle question the true enzyme nature of this and other 

 ' ' oxidases, ' ' which they look upon as organic peroxides, behaving like 

 other peroxides rather than as catalyzers. Practically the existence 

 of these bodies is demonstrated by their power to turn tincture of 

 guaiac blue, and they are, therefore, present in pus. 



Von Fiirth '"* sums up the situation in these words : "In the tis- 

 sues active catalytic agents, the peroxidases, are widely distributed; 

 which seem, just like the coloring matter of the blood, to be capable 

 of conveying the oxygen from peroxides to very readily oxidizable 

 substances. We find too in the statements bearing upon the oxy- 

 genases, the aldehydases and indophenoloxidases, occasion for .assum- 

 ing that there are substances in the tissues charged with oxygen w^hich 

 are able to give this off to easily oxidizable matter ; and these we may 

 in a measure regard as peroxides. But that is all. We do not know 

 whether the peroxidases are ferments or not." 



By their conception of oxygenase and peroxidase Chodat and Bach 

 would displace entirely the idea of enzymes oxidizing directly, the 

 true "oxidases," which they consider mixtures of oxygenase and 

 peroxidase. There have been, in any event, a number of ferments 

 described that seem to possess distinct oxidative powers. As each 

 is quite specific in its action, oxidizing but one substance, or one 

 group of related substances, they are generally designated by the 

 name of the substances upon which they act. INIost studied of these 

 are aldehydase and tyrosinase. 



Aldehydase,**" which is characterized by oxidizing aldehydes, par- 

 ticularly salicyl-aldehyde. According to Jacquet, this enzyme is so 

 intimately bound with the cell that it cainiot be obtained in extracts 

 until after the cells are dead, but is present in expressed cell-,iuices. 

 It can be isolated by the usual methods, is destroyed by boiling, acts 

 best when no free oxygen is present, and its action is inhibited by 

 CNII. It has been demonstrated in nearly all organs and tissues 

 exce])t pancreas, muscle, marrow, and mammary gland ; it is present 

 in the blood in snudl aiiKiunts. but not at all in the l)ile. It is most 



*>" BattclH and Stern do not include aldeliydai^o anion<,' tin- oxidizinj; cn/ynips. 

 on the ground tliat its action is not oxidative but hydrolytic. 



