1904] 



Studies on Enzyme Action. 



oil 



II, IY, VII, XI). The duration of these periods is conditioned by 

 the relation which the amount of enzyme present bears to the sugar, 

 the linear period disappearing when the amount of enzyme present is 

 relatively considerable (Tables I, III, VIII). It will be noted that in the 

 •cases studied in which the action proceeds comparatively slowly, e.g., 

 hydrolysis by lactase, emulsin or maltase — K falls rapidly in value ; 

 whereas when the action proceeds rapidly, e.g., hydrolysis by invertase 

 ■or diastase — K increases. 



To understand the origin of these differences, it is desirable to 

 consider the subject of mass action somewhat in detail, even at the risk 

 of repetition. 



Changes such as that which cane sugar undergoes in an aqueous 

 solution under the influence of a catalyst, in which, on account of its 

 large relative mass, the part played by the solvent may be disregarded 

 — known as changes of the first order — are assumed to follow the 

 logarithmic law of mass action : it is supposed that the one substance 

 only undergoes change and that the same fraction of the residue is 

 changed in successive equal intervals of time, i.e., the factor K deduced 

 1 S 



rom the equation K = — log is a constant. 



t o — x 



But this is an ideal conception, as it involves the assumption that the 

 amount of catalyst functioning is so small as to be negligible. In 

 actual practice, not only is the amount of enzyme used not incon- 

 siderable but it is known that the rate of change is affected both by 

 alteration in the concentration of the hydrolyte and in the proportion 

 which the hydrolyte bears to the catalyst ; moreover, the products of 

 change are known to exercise an influence and in concentrated solutions 

 reversion may take place. 



In view of the proof afforded by E. Fischer's researches that a close 

 relationship exists in configuration between the hydrolyte and the 

 enzyme which alone affects it, there can scarcely be any doubt that 

 hydrolysis by enzymes, in the first instance, involves the combination 

 of the enzyme with the hydrolyte, as Horace Brown and Glendinning 

 have assumed to be the case. 



On this assumption, the rate at which the change proceeds will 

 depend on the extent to which the combination of enzyme with sugar 

 takes place as well as on the degree of readiness with which the 

 compound breaks down. 



The proportion of the total sugar present in solution combined with 

 the enzyme and undergoing change at any one moment may be regarded 

 as the active mass of the sugar. The conception of an active mass has 

 already been introduced by Arrhenius* but in another connection — to 

 account for the very rapid rise in the value of K, when cane sugar is 

 hydrolysed by acids, occasioned by a rise in temperature, the increase 

 * ' Zeit. Phys. Chem.,' 1889, vol. 4, p. 226. 



