68 ENZYMES 



appears on reduction of tlie 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 therniostabile, the other therrnolabile, recalling the reaction of 

 complement and amboceptor. Strassner" found evidence that the .SH groups of 

 the tissues are responsible for the reduction of methylene blue; their activity 

 is impaired by heating, but a thermostable element of tissues augments the re- 

 ducing acti\ity of SH compounds, thus corroborating and explaining the observa- 

 tions of Ricketts. Harris,'* however, believes that the evidence for the existence 

 of a true reducing enzyme is as good as for most other cellular enzj-mes. An en- 

 zyme has been found in the liver, muscle and kidney which transforms aceto-acetic 

 acid into l-/3-oxybutyric acid, and called ketoreductase (Friedmann and Maase)." 



Oxidizing Enzymes in Pathological Processes. — Although the 

 oxidizing enzymes undoubtedly play an important part in pathological 

 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 «-hen the liver 

 undergoes self-digestion, which speaks against Spitzer's contention that 

 oxidase is a nucleoprotein.^° Schlesinger^^ found that it is less in 

 amount in livers of children dead from gastro-intestinal diseases than 

 in normal livers, as also did Brtining."*^ I am inclined to believe that 

 fatty metamorphosis, when brought about by poisons, is often due 

 to inhibition of the oxidizing enzymes (v. fatty metamorphosis), 

 although I found that livers the seat of the most profound fatty de- 

 generation showed no evident impaiiment of their power to oxidize 

 xanthine and uric acid.'^^ Buxton'*^ failed to find in tumors any en- 

 zyme giving the guaiac test alone, but found enzymes that did so in 

 the presence of H2O2 (peroxidases). Catalase was present, but no 

 very positive reactions for oxidizing enzymes w^ere obtained by the 

 indo-phenol reaction, the hydrochinon reaction, or with tjTosine for 

 tyrosinase, v. Fiirth and Jerusalem''^ have found evidence that the 

 melanin of melanotic tumors of horses is produced by tyrosinase. 

 Peroxidase has been demonstrated in the granules of pus cells (Fisehel) . *^ 



Meyer ^^ found that leucocytes, whether from pus or leukemic or 

 pneumonic blood, contained a substance oxidizing guaiac directly, 

 without the presence of H2O2, which is not liberated until the cells 

 are destroyed. By microchemical reactions oxidases have been found 

 present in the myelocytes and nucleated erythrocytes in leukemia, be- 



'^ Jour, of Infectious Diseases, 1904 (1), 590. 



" Biochem. Zeit., 1910 (29), 295. 



=8 Biochem. Jour., 1910 (5), 143. 



="» Biochem. Zeit., 1912 (27), 474; 1913 (55), 458. 



*" Duccheschi and Almagia (Arch. ital. Biol., 1903 (39), 29) also found the 

 aldehydase in livers of phosphorus poisoning usually no less abundant than in 

 normal livers. 



*' Hofmcister's Beitr., 1903 (4), 87. 



*-^ Monat. f. Kinderheilk., 1903 (2), 129. 



"Jour. Exper. Med., 1910 (12), 607 



** Jour. Med. Research, 1903 (9), 350. 



^6 Hofmeister's Beitr., 1907 (10), 131. 



"Wien. klin. Woch., 1910 (23). 15.57. 



<' Munch, med. Woch., 1903 ('A)), 14S9. 



