1919] 



DODGE TYROSINASE REACTION 81 



enzyme. Wolk ( '12) first suggested the possibility of two dis- 

 tinct enzymes but offered no proof. Beijerinck ('13) offered 

 the first definite proof that two distinct enzymes exist and 

 suggested that nitrogen is split from the tyrosin molecule 

 during the reaction. In the course of the isolation of certain 

 soil organisms he noted that black spots were produced on 

 tyrosin agar plates, wherever small transparent colonies were 

 growing over the more deeply located colonies of "Acti- 

 nomyces." On isolating each organism separately he was 

 unable to find pigment production with either, but on cross- 

 ing the streaks on agar the coloration was again produced. 

 This with similar experiments led him to conclude that there 

 were two enzymes involved, one being present in each 



organism. 



Chodat and Schweizer (13) showed that an enzyme ex- 

 tract from the potato split carbon dioxide and ammonia from 

 glycin, leaving formaldehyde, but failed to show that this is 

 a specific property of tyrosinase, the enzyme which gives the 

 red and black colorations with tyrosin. Their work was 

 wholly qualitative, carried out in solutions of varying de- 

 grees of alkalinity. Toluol was the antiseptic used, and ap- 

 parently only a small amount of that. Folpmers ('16) at- 

 tempted to isolate the products and succeeded in isolating 

 benzaldehyde by the formation of benzylidene-para-nitro- 

 phenyl-hydrazone. Phenylalanin and tyrosin gave too small 

 quantities to be determined with certainty. 



I regret that I have been unable to see the work of 

 Schweizer ('16), but, according to his reviewers, he finds the 

 amino group split off and the side chain oxidized, as succes- 

 sive steps in the action of a single enzyme, tyrosinase. In the 

 work detailed below, no deamination could be found which 

 could be ascribed to enzyme action, although the character- 

 istic colorations with tyrosin were obtained. A much simpler 

 explanation for these phenomena seems to lie in consider- 

 ing that one is working with a mixture of enzymes, and that, 

 in the case of the Geneva workers where the work was done 

 largely with enzymes from a single source, a deaminase or 

 deaminases were present as well as the enzyme, giving the 



