1913.] Processes Operative in Solutions and Enzyme Action. 573 



If both the carboxylic radicle and the amino-radicle to which the carbo- 

 hydrate radicle is coupled formed part of some one amino-acid residue in the 

 colloid complex, they would be in close conjunction and therefore self- 

 protective ; the " resting " enzyme may be thought of, in fact, not as an acid 

 proper but as an internal salt of tbe glycine type : — 



Aminoacetic acid Glycine 



X NH 2 NH 3 



CH 2 < CH 2 < \ 



N COOH X C0.0 



To unlock and render the " zymogen " active, it would be necessary to add a 

 substance of superior acidic power — just as in the case of an indicator, which 

 " indicates " only when either an acid or an alkali is added which is of 

 superior strength. 



It will be obvious that if brought into the proper apposition the molecule 

 of an a-glucoside would fit the a-enzyme and the molecule of a /3-glucoside 

 the /3-enzyme shown above and would fit it in such manner, moreover, that 

 not only would contact be secured over the carbohydrate surface but the 

 junction at which hydrolysis takes place in the glucoside would be in close 

 proximity to the carboxylic radicle in the enzyme : it cannot be doubted 

 that if an electrolyte intervened, hydrolysis would at once take place in such 

 a system. The manner in which the electrolyte operates in such cases has 

 been discussed in S. XXIV, p. 617, § 26. 



In amplification of the argument advanced on p. 571, it may be pointed 

 out that if each enzyme particle, in virtue of its colloid character, tend to 

 absorb the hydrolyte so that the solution at its surface is 

 relatively concentrated, the concentrated layer (b) would 

 necessarily extend across the active enzymic area (a), as 

 may be illustrated thus : — K 



The mechanism postulated is therefore such that the con- 

 centration of the hydrolyte would be raised and preserved 

 in the neighbourhood of the active enzymic centre. 



Action of Acids and Alkalies. — If we seek to interpret the effects produced 

 by enzymes in the light of the hypothesis now advocated, it is obvious that 

 one of the main conditions to be fulfilled is the maintenance of the freedom 

 of the acidic (or alkylic) radicle which is the active hydrolytic agent. 



It is probable that the amount of actual enzyme present in the prepara- 

 tions which are ordinarily used is so minute that the quantity of acid 

 (or alkali) which would render it active initially, assuming that it is present 

 either as an internal or as an ordinary salt, must be very small : therefore, if 



