580 Dr. Armstrong and Prof. Armstrong. Studies on [June 13, 



that the degree of concentration is soon reached at which an enzyme has 

 maximum activity. 



As already remarked, the course of change is in no way that to be expected 

 if the action be a mass action effect. 



Y. Henri gives abundant proof in his comprehensive memoir* that the 

 activity of enzymes such as invertase, emulsin and diastase falls off" as tbe 

 concentration of the solutions is increased beyond a certain limit — about 

 half volume-normal strength in the case of cane sugar. The observations of 

 all other workers support this view. 



In our work on urea, numerous instances are given showing that the 

 enzyme is more effective in the weaker solutions. 



The following results obtained with a-methyl glucoside and a-glucase 

 (yeast extract) also afford evidence that, instead of increasing, the activity 

 of the enzynie soon reaches a superior limit and then diminishes as the 

 concentration is increased. 



Concentration of glucoside 



Weight of glucose produced 



M/2 (9 '7 grm. per 100 gnu. water) 



grm. 



grm. 



2 -16 



2 -21 



M (19-4 „ „ ) 



2 -37 



2 -35 



3M/2 (29-1 „ „ ) 



2-15 



2-25 



2M (38-8 „ „ ) 





1 -98 



The diminution in the activity of the enzyme caused by an increase in the 

 concentration of the hydrolyte beyond a certain point is to be set down, we 

 believe, mainly to changes in what may be termed broadly the osmotic state 

 of the solution — to changes in the state of the solvent which affect the state 

 of " hydrolation " both of enzyme and of hydrolyte. 



According to the hypothesis advocated in several previous communications, 

 as the concentration of the solution is increased, the extent to which the 

 surfaces of the enzyme and of the hydrolyte are hydrolated effectively must 

 vary and must diminish as the concentration is increased beyond a certain 

 maximum : consequently, the reciprocal activity of enzyme and hydrolyte 

 must vary and must diminish so soon as the degree of concentration is 

 exceeded at which the degree of hydrolation ceases to be that which is most 

 favourable to the occurrence of change. 



In no other way does it appear to us to be possible to account for the 

 marked effect which an increase in the concentration of the hydrolyte has 

 in diminishing the rate at which change takes place — the effect being both 

 beyond that which is to be expected to arise from a reversal of the change 

 * ' Lois generates de l'Action des Diastases,' Paris, 1908. 



