PHYSIOLOCAL OXIDATION PKOCESSES. 875 



oxidase, xanthin oxidase (see below) belong, are soluble in water, re- 

 sistant to alcohol and acetone and can be heated to 55-60 C. The 

 oxodones, which for example oxidize succinic acid to malic acid and 

 act upon p-phenyldiamine, cannot be extracted from the tissues by water; 

 they are injured or destroyed by alcohol, acetone or by being heated 

 to 55-60 C. 



WARBURG J has carried on extensive experiments on the influence of 

 foreign bodies upon the respiration in the cells and has conformed the 

 results to OVERTON'S theory of lipoid membrane. 



No deep oxidation processes have been produced under the influence 

 of the mentioned oxidizing substances outside of the organism. The 

 various divergent views on the nature of the oxidizing substances strik- 

 ingly indicates how little exact knowledge we have of this subject. 

 Perhaps the oxidation within the body takes place step by step, and it 

 seems possible that the consecutive stages of the reaction can be brought 

 about by different agents. A positive division of the so-called oxidizing 

 enzymes cannot be made at the present time. For in many cases it 

 is undecided whether we are dealing with enzymotic processes or with 

 non-enzymotic catalytic action of metallic salts, especially as the 

 reports on the heat-resistance of the active substances are contra- 

 dictory. In the enzymotic oxidations we are in many cases in doubt 

 whether the oxygen is transported directly to the oxidizing substance or 

 whether the oxidation is brought about by the system peroxide plus 

 peroxidase. When the oxidation cannot be shown as due to the just- 

 mentioned system, then the active enzyme is called simply oxidase. 



In consideration of the substances upon which the oxidation enzymes act, 

 we can divide them for the present into the following groups, according to 



OPPENHEIMER: 2 



1. Alcoholases, which transform alcohols into acids, for example the acetic- 

 acid-forming enzyme of certain varieties of bacteria. 



2. Aldehydases, which oxidize aldehydes into acids, for example, salicylase. 



3. Purine-oxidases, which oxidize hypoxanthine and xanthine into uric acid and 

 which act upon uric acid with the formation of allantoin. This last reaction is 

 produced by the action of the so-called uricase. 



4. Phenol-oxidases, which oxidize various phenols and related bodies with the 

 formation of pigments. The guaiac reaction is of this kind. 



5. Tyrosinases, which oxidize tyrosine and closely related bodies into dark 

 pigments. 



The system peroxide -f peroxidase has been shown only in connection with 

 enzymes of group 4. 



Besides the above-mentioned bodies, upon which the different classes of oxidiz- 

 ing enzymes act more specifically, we can mention the following as oxidase reagents. 



^eitschr. f. physiol. Chem., 67, 69, 70, (1910); 71, 76 (1911). 



8 Die Fermente und ihre Wirkungen, 3. Aufl., Spec. Teil, 351 (1909). 



