1913.] Processes Operative in Solutions and Enzyme Action. 569 



is effective within a particular region, not over its whole surface, it is only 

 necessary that the hydrolyte should be determined to this active region. 



The partial or complete saturation of the surface of the colloid particles 

 would serve, therefore, to promote the maintenance of a sufficiently constant 

 supply of hydrolyte to this special region. 



The hydrolyte attached to the acceptor, however, would not be permanently 

 held but would oscillate between it and the liquid, so that only a certain 

 proportion of effective contacts would be made — contacts during which the 

 circuit would be completed wherein hydrolysis could and did take place. The 

 rate of change would be determined by the rate at which these effective 

 contacts occurred but would be relatively slow, in all probability. 



After discussing the matter with Dr. Horace Brown, who has given special 

 attention to such problems, we are inclined to think that the rate at which 

 liquid diffusion takes place is probably so great that it is not necessary to 

 take this into account as a limiting factor. 



Influence, of 'the Prochtcts of Change. — As the products of change accumulate 

 in the solution, they affect the enzyme in various ways. It is to be supposed 

 that the product immediately allied to the acceptor enters directly into 

 competition with the hydrolyte and more and more takes its place as the 

 amount present becomes greater. The carbohydrates and many glucosides 

 are cases in point. 



Products having no special configurational relationship to the acceptor 

 section of the enzyme may act upon it in various other ways such as the 

 following : — 



(a) By neutralising it, as in the case of urease and doubtless also of pepsin 

 and trypsin. 



(b) By converting it into a derivative which is different in structure and 

 no longer compatible with the enzyme — the action of some aldehydes and of 

 quinone are cases in point. 



(c) By changing the osmotic conditions in the solution and thereby altering 

 the state of " hydrolation " at the enzymic surface of the acceptor and also of 

 the agent. Probably any substance dissolved in the solution will act to some 

 extent in this manner but such effects are specially noticeable in the case of 

 " inert " materials such as the alcohols (hormones). The diminution in the 

 rate of change winch is noticeable when the concentration of the hydrolyte 

 exceeds a certain maximum is to be accounted for, apparently, in this way. 

 In explanation of this contention, we may point out that it is based on the 

 assumption that in aqueous solutions all interactions take place at hydrolated 

 surfaces — in other words, we regard both acceptor and hydrolyte as hydrolated 

 and assume that they are brought into conjunction at their hydrolated surfaces. 



