1904] 



Studies on Enzyme Action. 



501 



only when it is modified by the products of change be accepted, it 

 follows that the interaction does not take place at any time in accord- 

 ance with the law of mass action. 



Somewhat later, an elaborate investigation of the action of enzymes 

 was carried out by Victor Henri, whose work is summarised in his ' Lois 

 generales des diastases,' Paris, 1903. Henri found that the velocity 

 coefficient K, calculated on the assumption that the logarithmic law 

 was applicable, steadily increased in value as the action proceeded. He 

 attributed the increase to the influence of the products of change 



(^j and took these into account by writing Ki + € in place of K 

 in the equation of mass action, which thus becomes 



!- K *.( 1+ «i)< 8 -'>- 



This expression was derived from Ostwald's 1 Lehrbuch.'* It may be 

 pointed out that it is there put forward as applicable to cases of change 

 in which the products may be assumed to have an accelerating influence, 

 and that, as a matter of fact, it is the equation to a curve showing- a 

 change in direction corresponding to a rise to a maximum velocity and 

 a subsequent fall in the rate. Henri deduced from his results the 

 value + 1 for e, so that the equation became 



2Ki = - log — — . 

 t 6 S-x 



In 1902, Adrian Brown, f besides arriving at the conclusion that 

 hydrolysis is effected at a more rapid rate than is indicated by the law 

 of mass action, also showed that on varying the concentration an 

 approximately constant weight — not as the law of mass action requires a 

 constant proportion — of sugar is hydrolysed in a given time. It is 

 necessary to bear in mind, however, that in his experiments, the 

 proportion of the total sugar hydrolysed in no case exceeded one-fifth, 

 so that in reality the comparison was made only during the earlier 

 stage of the hydrolysis. To explain the somewhat remarkable result 

 to which he was led, Adrian Brown assumed that not only is a 

 compound of enzyme and sugar formed but that this persists during a 

 really appreciable interval of time : consequently a molecule of the; 

 enzyme can effect only a limited number of complete molecular changes 

 in unit time ; whatever the available mass may be, no increase in 

 the amount of substance changed is possible. On the other hand, in 

 dilute solutions in which the proportion of sugar to enzyme falls below 

 a certain maximum, the amount of sugar hydrolysed should be directly 

 proportional to the amount present — and this Adrian Brown proved ta 

 be the case. 



* 2nd edition, vol. 2, p. 264. 



f * Chein. Soc. Trans.,' vol. 81, p. 373. 



2 N 2 



