PROTEOLYTIC ENZYMES AS CATALYSORS 393 



must accelerate, and accelerate equally, the attainment of that 

 equilibrium from either side; it must in other words accelerate 

 the forward and the reverse reactions equally. This is readily 

 seen when we reflect that equilibrium in the reacting system is 

 attained when the velocity of the forward is equal to that of the 

 reverse reaction. If the velocity of the forward reaction is 

 increased by any agency, therefore, and the station of equi- 

 librium is unaffected, the velocity of the reverse reaction must 

 also have been increased and in the same proportion. The 

 correctness of this theoretical deduction has also been established 

 in a number of "typical" instances of non-fermentative catalyses, 

 but although it has been shown that yeast (58) (59), kephirlactase 

 (28), diastase (22), emulsin (24), lipase (7) (65) (55) (9) (130) 

 (132) (98) (99), trypsin (135) and pepsin (108) (109) (111) (112) 

 (35) will not only accelerate the hydrolysis of maltose, lactose, 

 glycogen, amygdalin, fats, protamin and paranuclein, respec- 

 tively, but also the synthesis of these substances from the prod- 

 ucts of their hydrolysis, yet it has in no instance been shown 

 that the velocity of the reverse reaction is accelerated in the 

 same proportion as that of the forward reaction; indeed such 

 evidence as exists tends to show that this is not the case (14) 



CUD. 



From the study of a limited number of instances of non- 

 fermentative catalysors, however, it appeared, as I have said, 

 that the catalysors are substances which remain unchanged at 

 the end of the reaction which they accelerate and which do not 

 shift the station of equilibrium and therefore cannot initiate, 

 but only accelerate reactions (89) (90) (91) (92) (93). 



Recent investigations, particularly those of Stieglitz (127) (128) 

 and Euler (27), have shown that the above definition of catalysis 

 is too rigid and that the cases which it adequately covers are 

 merely extreme instances of a much more general phenomenon. 



It has long been known that in many instances of unquestioned 

 catalysis the acceleration of the reaction in question is accom- 

 plished, or at least accompanied by, the formation of inter- 

 mediate compounds between the substrate and the catalysor. 

 The classic illustration of a catalysed reaction of this type is 

 that afforded by the "continuous etherification process" for the 

 production of ether from alcohol. In this process sulphuric 

 acid is employed as catalysor and, as is well known, the sulphuric 



