74 ENZYMES 



ceived extensive study, which will he found fully described in the 

 monograph b}' Kastle {loc. cit.) '^* and under the appropriate subjects 

 in subsequent chapters. 



Other Oxidizing Enzymes. — Of the great numlier of other less 

 studied oxidizing enzj-mes little can be definitely stated. Some con- 

 sider that they are largely different manifestations of the action of 

 one oxidizing ferment, but against this view Jacoby mentions that they 

 occur distributed unequally in different organs, can be separated from 

 each other, and they cause different reactions. For the catalase and 

 for laccase (which produces the Japanese lacquer by an oxidizing 

 process) and perhaps for other oxidizing ferments, iron and man- 

 ganese may be essential constituents. Of particular significance for 

 pathology are the enzymes which accomplish the oxidation of purines 

 to uric acid and the subsequent destruction of uric acid. These are 

 discussed in Chapter xxi. Also the enzymatic oxidation and reduc- 

 tion of ^-oxj^butyric acid and aceto-acetic acid in the liver, as studied 

 by Dakin and Wakeman,"^ are of great importance in acidosis {q. v.). 



Reducing enzymes have not yet been satisfactorily demonstrated."* 

 It is possil)le that they do not exist, and that the intracellular re- 

 ductions that are carried on within the cells are brought about by 

 simple chemical reactions independent of catalysis. The best known 

 intracellular reduction is that of methylene blue, which can be readily 

 studied experimentally because the blue color disappears on reduction 

 of the dye. It is open to question if this particular reduction is due 

 to a reducing enzyme. According to Ricketts ^^ the reduction depends 

 upon two bodies, one thermostabile, the other thermolabile, recalling 

 the reaction of complement and amboceptor. Strassner ^"^ found evi- 

 dence that the SH groups of the tissues are responsible for the reduc- 

 tion of methylene blue ; their activity is impaired by heating, but a 

 thermostable element of tissues augments the reducing activity of SH 

 compounds, thus corroborating and explaining the observations of 

 llicketts. Harris,"^ however, believes that the evidence for the exist- 

 ence of a true reducing enzyme is as good as for most other cellular 

 enzymes. An enzyme has been found in the liver, muscle and kidney 

 which transforms aceto-acetic acid into l-/3-oxybutyric acid, and called 

 ketoroductase (Friedmann and Maase)."'^" 



Oxidizing Enzymes in Pathological Processes. — Although the 

 oxidizing enzymes undoubtedly play an important part in pathologi- 

 cal conditions, they have been but little investigated from this stand- 

 point. Jacoby found that they did not disappear from the degen- 

 erated liver in phosphorus poisoning or in diabetes, or when the liver 



03 Jour. .Amor. IVfod. Assoc, 1910 (54), 14-11. 



o4Soo TIofTtPr. Arc-li. exp. Path. u. Pharm.. lOOS, Suj)])!.. p. 25.3. 



"•"•Jour of Infoft.ions Disoaaos, 1004 (1), 500. 



(•« Biocliem. Zcit., 1010 (20), 205. 



"7 Biofiioni. .loiir., 1010 (5), 14:?. 



07a iJiocliom. Zeit., 1012 (27), 474; 101.3 (55), 4,58. 



