246 A SYMPOSIUM ON RESPIRATORY ENZYMES 



THE EFFECTS OF CERTAIN DIAMINES ON ENZYME SYS- 

 TEMS, CORRELATED WITH THE CARCINOGENICITY 

 OF THE PARENT AZO DYES 



C. J. KENSLER 

 Memorial Hospital, New York 



In 1935 Hashimoto (1) reported the isolation of acetyl-2-methyl-p- 

 phenylenediamine from the urine of rats fed the carcinogen, o- 

 aminoazotoluene. Another azo carcinogen, dimethylaminoazoben- 

 zene (butter yellow), the metabolism of which has been studied by 

 Stevenson, Dobriner, and Rhoads (2), has also been found to be 

 split in vivo at the azo linkage. The urine of animals fed butter 

 yellow contained aminophenol and p-phenylenediamine. The free 

 and acetylated forms of both compounds were found. No dimethyl-p- 

 phenylenediamine was isolated, but it may be assumed until evi- 

 dence to the contrary is presented that it is a precursor of the 

 excreted p-phenylenediamine. Orthoamidoazotoluene and dimethyl- 

 aminoazobenzene are the only carcinogenic azo compounds whose 

 metabolic breakdown has been studied. 



A previous report (3) from this laboratory presented evidence that 

 the concentration of diphosphopyridine nucleotide (Coenzyme I) 

 in the livers of rats fed dimethylaminoazobenzene is 60 per cent 

 less than in the livers of rats fed the same basal diet without the 

 carcinogen. This fact suggested that the administered dimethyl- 

 aminoazobenzene, or some metabolic breakdown product of it, might 

 depress in vitro the activity of a fermenting system from yeast in 

 which diphosphopyridine nucleotide is the limiting factor. Experi- 

 ment proved the validity of this suggestion. The methods and the 

 results obtained are presented in detail in a report which will appear 

 shortly (4). 



In brief, it was found that whereas the original carcinogen, butter 

 yellow, did not inhibit fermentation at all, the isolated derivative 

 of butter yellow, p-phenylenediamine, was strongly inhibitory, and 

 dimethyl-p-phenylenediamine, the supposed precursor of the simpler 

 compound, had an even more powerful toxic eflFect. 



In view of the results obtained with butter yellow and its break- 

 down products, it seemed desirable to test on the same feraienting 

 system the eflFect of chemically related substances. Dr. Leonor 

 Michaelis, who had previously prepared a large number of methyl 

 derivatives of p-phenylenediamine as a part of his general study 

 of two-step oxidations, generously provided samples of these com- 

 pounds for use in this investigation. Their inhibitory eflPects on the 



