80 ENZYMES 



(q. v.), in which the urine becomes dark upon exposure because 

 of the presence of homogentisic acid. 



Other Oxidizing Enzymes. Of the great number of other 

 less studied oxidizing enzymes little can be definitely stated. 

 Some consider 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 dif- 

 ferent reactions. For the catalase and for laccase (which 

 produces the Japanese lacquer by an oxidizing process) and 

 perhaps for other oxidizing ferments, iron and manganese may 

 be essential constituents. Bertrand l considers that laccase is 

 an organic manganese compound. 



Among these little known oxidizing ferments is one that 

 seems to act specifically on the purin bases, changing them into 

 uric acid (Spitzer 2 ), and one which destroys uric acid, in the 

 presence of catalase (Croftan 3 ). 



Reducing" enzymes have not yet been satisfactorily 

 demonstrated. It is possible that they do not exist, and that 

 the intracellular reductions that are carried on within the cells 

 are brought about by simple chemical reactions independent of 

 catalysis, or it may well be that the oxidizing enzymes in some 

 cases act reversibly ; this possibility does not seem to have been 

 investigated. 



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 4 the reduction depends upon two bodies, 

 one thermostabile, the other thermolabile, recalling the reaction 

 of complement and amboceptor. Johannsen 5 found the liver 

 most active in reducing m ethyl en e- blue, the kidney next. Ex- 

 tracts of the organs did not contain the reducing substance, 

 which seems to be bound to the cell elements. 



Oxidising Enzymes in Pathological Processes. 

 Although the oxidizing enzymes undoubtedly play an important 

 part in pathological conditions, they have been but little investi- 

 gated from this standpoint. Jacoby found that they did not 

 disappear from the degenerated liver in phosphorus poisoning 



1 Compt. Rend. Acad. Sci., 1897 (124), 1355. 

 2 Pfluger's Arch., 1899 (76), 192. 



3 Medical Record, 1903 (54), 6. 



4 Jour, of Infectious Diseases, 1904 (1), 590. 



5 Arb. aus d. path. Inst. Tubingen, 1905, vol. 5. 



