444 CHEMICAL DYNAMICS 



defined by the mono-molecular formula, terminating only when 

 hydrolysis is practically complete, the autohydrolysis, on the 

 contrary, which caseinates undergo in aqueous solution in the 

 absence of enzymes falls off in velocity with time much more 

 rapidly than would be indicated by the monomolecular formula, 

 so that the process comes to a stop when a very large proportion 

 of the protein is still unhydrolysed. The products of the tryptic 

 hydrolysis of casein exert, moreover, an almost negligible effect 

 upon the velocity of autohydrolysis, even when added in very 

 high concentration. We must infer, therefore, either that trypsin, 

 in dilute solutions, shifts the equilibrium between protein <=^ 

 products towards the right, or else that the rapid slowing-down 

 of the autohydrolysis is due to the attainment of a " false equi- 

 librium," i.e., an indefinite delay in the attainment of equi- 

 librium due to the interposition of a specifically slow reaction 

 in a series of catenary reactions, each one of which utilizes the 

 products of the preceding reaction. 



4. Reciprocal Catalysis. We have seen that enzymatic 

 synthesis of paranuclein A may occur at temperatures 10 to 15 

 degrees in excess of that at which the hydrolysing activity of 

 pepsin is rapidly and completely destroyed. This invites adop- 

 tion of the view, previously expressed by Euler (17) (18) that 

 the synthesizing and hydrolysing forms of the enzyme are not 

 identical. Euler believes that two varieties of every hydrolysing 

 enzyme exist, the one accelerating, primarily, hydrolysis, the other 

 accelerating, primarily, synthesis, and that under definite condi- 

 tions a definite equilibrium exists between the two enzymes. He 

 bases this view, in the main, upon the non-constancy of the 

 velocity-constant of certain enzyme-accelerated reactions with 

 varying substrate-concentration, and upon the non-identity of 

 the synthesized product (isomaltose) derived by the action of 

 maltase upon concentrated glucose with the maltose from which 

 the glucose was derived by hydrolysis, and of the product (iso- 

 lactose) obtained by the action of lactase upon a concentrated 

 solution of galactose and glucose with the lactose from which 

 the galactose and glucose are derived.* Euler believes that the 

 " anti-trypsins " found in -serum and in egg-white are simply the 

 synthesizing form of the enzyme and that the anti-pepsin and 



* It is stated, however, that even sulphuric acid, acting upon a concentrated 

 solution of glucose, gives rise, not to maltose but to isomaltose (19). 



