ORIGIN AXD MAINTEN. OF OFT. ACTIVITY 



39 



>- 



> 



H 

 O 

 < 



_J 

 < 



o 



I- 



Q. 

 O 



TIME — *■ 

 Fig. 3. Change in optical activity, as a function of time, in the enzymatic 

 asymmetric synthesis of the nitrile of mandelic acid (from Kulm, 1936). 



that the addition of the latter accelerates the reaction and 

 gives to it an asymmetric character but does not influence 

 its equilibrium constant. 



These observations made it possible for Werner Kuhn 

 (1936) to undertake the theoretical analysis of the prin- 

 ciples of the asymmetric synthetic action of enzymes. We 

 shall summarize here his more important conclusions. 



It should be pointed out, first, that the separated active 

 components of a given organic substance and the equi- 

 molecular mixtures of these components (racemates) are 

 not equivalent from the thermodynamic point of view. 

 The mixing of the components into a racemate liberates 

 energy, while their separation requires an expenditure of 

 work. Consequently the optically active state is not a 

 state of equilibrium as compared to the racemic state. 

 The question arises, then, as to the manner in which such 

 conditions of thermodynamic disequilibrium can be real- 

 ized in catalytic reactions in living matter. One might 

 first inquire whether such reactions are true catalytic 

 reactions or not. 



Let us consider the characters of a true catalysis lead- 

 ing to the formation of an asymmetric compound. Inas- 

 much as the preparation of the left and that of the right 

 antipode of a given substance in equal concentrations are 

 equivalent from the standpoint of energy expenditure, the 



