1912.] 



Studies on Enzyme Action. 



121 



one with the unneutralised liquid, the other after neutralising it by adding 

 the equivalent amount of alkali or acid. The results are given in Table V. 

 It will be noticed that the acid but not the ammonia had a distinct influence 

 in promoting decay of the enzyme. 



The effect was found to be more marked in more strongly acid or alkaline 

 solutions. The results given in Table VI show, however, that though the 

 presence of ammonia influences the activity of the enzyme, decay takes place 

 only gradually. 



Table VI. 





Percentage of urea hydro] 



ysed in 





mixtures of 20 c.c 



. enzyme 



solution 





and 20 c.c. 2M/5 urea solution 



Enzyme solution. 





in 1 hour at 25°. 







Initial. 



1 day. 





4 days. 



Aqueous solution of 10 per cent, of Soja extract [kept] 



26 -4 



24-9 



25 -3 



21 -4 



N/25 HC1 solution of 10 per cent, of Soja extract 



2-6 









!N/25 NH 3 solution of 10 per cent, of Soja extract [kept] 



19-2 



15 -2 



13-1 



8-9 











8-8 



Ditto saturated with COo at time of experiment 









18 -3 



The experiments appear to justify the conclusion that the effects produced 

 initially by ammonia are at least mainly clue to the influence it exerts on the 

 change itself and that there is no reason to suppose that the enzyme is 

 destroyed by it, to any serious extent, either in the first instance or during 

 the course of an experiment lasting a short time. 



Influence of Carbon Dioxide. — Inasmuch as carbonate of ammonia has a very 

 slight inhibiting effect in comparison with that of ammonia, it was to be 

 supposed that carbonic acid would serve to neutralise, almost if not entirely, 

 the effect ammonia produces. Having formed the opinion that the ammonia 

 acted as an alkali and was in some way opposed to the urea, we therefore 

 made the experiment in the full expectation that it would exercise a positive 

 influence ; we were not prepared, however, to find that carbonic acid has so 

 marked an influence in promoting and increasing the activity of the enzyme 

 as our experiments show that it has. The results of a pair of experiments 

 are represented in the uppermost pair of curves in the lower graph on 

 p. 119 and in Table VII. 



In making these experiments, the behaviour of an M/5 solution of urea 

 containing 25 c.c. of Soja extract was contrasted with that of a solution 

 of the same strength prepared by saturating the liquid with carbon dioxide 

 prior to adding the enzyme and then maintaining the passage of a current 



