ORIGIN AND MAINTEN. OF OPT. ACTIYITY 47 



eoiislv, the remainder of the untranst'ormed substances 

 will undergo a" corresponding decrease in optical purity.) 



Langenbeck and Triem (1936) proved experimentally 

 that the optical activity can be increased in reactions of 

 this type. They synthesized /-tyrosine anhydride from 

 /-tyrosine methyl ether and observed a concentration of 

 30.8% of /-tyrosine in the final product while the initial 

 substance contained only 27.4%. 



It is possible that such processes have taken place in 

 the enzymatic origin of ferments, that is, when one fer- 

 ment has been synthesized wdth the aid of another opti- 

 cally active ferment. Then the necessary decrease of 

 optical purity of the initial material is of no importance 

 since only the newly formed ferment, in the interrupted 

 reaction, will transmit to some other substance its 

 increased optical purity. 



It should be noted, in relation with the reactions 

 described in this section, that the succession of synthetic 

 processes which take place continuously in living systems 

 might in itself be an important factor in the evasion of 

 the effects of racemization. The incessant reconstruction 

 of living matter should then, perhaps, be considered as 

 an indispensible condition for the maintenance of the 

 optical purity of stereo-autonomic substances. 



It is usually thought that, though nature might evade 

 for a time the eifects of racemization, finally the latter will 

 inevitably set in and that nature does not possess any 

 method of correction by which it would remove the un- 

 natural isomer and actively resist racemization. Kuhn 

 (1936) not only accepted the idea of the absence of such 

 active resistance, there being no enzyme know^n for per- 

 forming this function, but he thought that the racemiza- 

 tion which finally takes place might constitute, in part, the 

 process of ageing. 



The fact that, when animals and plants are fed with 

 racemic amino-acids, they principally consume the natural 

 isomers of the left steric series and leave the other isomer 

 intact, has been, in general, considered as proving that the 



