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Arthur L. Koch 



The activity in various fractions was differently affected by caffeine and this 

 effect was different in acid and at neutrahty and at alkaline reaction (see Table 

 II). This finding explains the relatively low toxicity and bacteriostatic power 

 of the plant alkaloids. 



Table II. Inhibition of Inosine Arsenolysis by Caffeine 



* Enzyme Preparation 6-1 was most active at pH 5, preparation 6-2 at pH 9, and preparation 

 6-3 at pH 7. 



In more recent work (13) three new enzymes have been demonstrated in 

 extracts of this organism: an inosine hydrolase, a purine-pyrimidine trans- 

 ribosidase, and a purine-purine transribosidase. All are inhibited to some 

 degree by various purines. The results of the enzymatic studies are summarized 

 in Table III. 



V. WORKING HYPOTHESIS 



The mutagenic agents do inhibit enzymes that appear to be directly linked 

 to the path of nucleic acid synthesis, but how can such an interference affect the 



