66 ENZYMES 



enzymes or enzyme-like substances that come more properly under the 

 head of oxidases or oxidizing enzymes. Battelli and Stern contend 

 that the only real oxidases which have yet been completely established 

 are: 1. Polyphenoloxidases (oxidizing phenols and their amino com- 

 pounds, but not tyrosine); 2. Tyrosinase; 3. Alcohol oxidase; 4. 

 Xanthine oxidase; 5. Uricase. Chodat and Bach believe that the 

 enzymes which are designated above as polyphenoloxidases have a com- 

 plex structure, consisting of peroxidase and oxygenase. ^^ Mathews^* 

 holds that "under the term oxidases there have been confused two 

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

 more important class, which activates, by dissociation, the reducing 

 substances. 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 oxida- 

 tion by activating peroxides, and is quite distinct from catalase and from the other 

 oxidases. The peroxide on wluch 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. Loevenhart and Kastle ques- 

 tion the true enzyme nature of this and other "oxidases," which they look upon as 

 organic peroxides, behaving like other peroxides rather than as catalyzers. Prac- 

 tically tlie existence of these bodies is demonstrated by their power to turn tinc- 

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



Von Fiirth^^ sums up the situation in these words: "In the tissues active cata- 

 lytic agents, the peroxidases, are widely distributed; which seem, just like the 

 coloring matter of the blood, to be capable of conveying the ox3^gen from peroxides 

 to very readily oxidizable substances. We find too in the statements bearing 

 upon the oxygenases, the aldehydases and indophenoloxidases, occasion for assiun- 

 ing that there are substances in the tissues charged with oxygen which 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 thej^ act. Most studied of these are aUlehytlase and 

 tyrosinase. 



Aldehydase,^^ which is characterized l)y oxiilizing aldehydes, particularly 

 salicyl-aldehydc. According to Jacquct, this enzyme is so intinuitely bouutl with 

 the cell that it cannot l)e olitained in extracts until after the cells are dead, but is 

 present in expressed cell-juices. It can be isolated by the usual metliods, is de- 

 stroyed by boiling, acts best when no free oxygen is present, and its action is in- 

 hibited 1j3' CNH. It lias been demonstrated in nearly all organs and tissues except 

 pancreas, nuiscle, marrow, and mammary gland; it is present in the blood in small 

 amounts, but not at all in the bile. It is most abundant in the liver-*^ and spleen, 

 and is present in jjig embryos, 9 cm. long, but not in tliose 2-3 cm. long. Jacoby 

 has obtained a body with the properties of aldehydase which did not give protein 

 reactions. It is a true enzyme, since it o.xidizes aldeliydes without itself being 



^' See also Onslow, Biochcm. Jour. l'.)l'.) (13), 1. 

 ^-i Jour. Hiol. Chem., 190<J ((>), 1. 



■■'^ Battelli and Stern do not include aldeliydase among the oxidizing enzymes, 

 on the ground tliat its action is not oxidative but liydrolj-tic. 

 ^o BatteUi and Stern, Biochem. Zeit., 1910 (29)," 130. 



