126 IMMUNO-CATALYSIS 



be inquired as to whether the cellular enzymes which catalyze one- 

 sided asymmetric synthesis or metabolism (i.e., either 1- or d-isomer) 

 of optically active substances are themselves optically active.* It has 

 been claimed (Helferich, et ah, 1938) that ;8-d-glucosidase and 13-d- 

 fructosidase contain carbohydrate-like substances of glucose nature; 

 and it is postulated that these enzymes by virtue of the carbohydrate 

 groups, perhaps with iS-con figuration, combine with and catalyze 

 mirror image substrates. The active group of the enzyme is assumed 

 to form a racemate with the substrate in accordance with the "Lock 

 and Key" idea of Emil Fischer (Emil Fischer, 1894, 1898; see also 

 Lettre, 1937). These claims and postulates though of utmost theo- 

 retical interest are not as yet experimentally demonstrated. 



On the other hand, it has been definitely shown that optically ac- 

 tive d- and 1-active organic catalysts orient specifically the configura- 

 tion of the atomic groups on asymmetric carbon atoms produced during 

 the synthesis of optically active substances from optically inactive start- 

 ing materials. By an accurate consideration of these laboratory proc- 

 esses, which take place continuously in the living cell, we might be 

 able to understand at least the principles involved in asymmetric 

 synthesis. t 



Rosenthaler (1908, 1909, 1913) obtained the first proof that an 

 enzyme in emulsin which he presumed to be optically active could 



* Pasteur suggested that every asymmetry owes its existence to some asymmetric 

 forces operating at the moment at which the asymmetry appeared. Emil Fischer ( 1 894, 

 1898) stated that one active molecule gives rise to another, and the formation of 

 sugar in plants takes place by chlorophyll which he assumed to be optically active. 

 The optical activity of chlorophyll has recently been demonstrated by Stoll and 

 Wiedemann (1933). 



tin evaluating the reports concerning the optical purity of an enzymic system or 

 asymmetric synthesis with a preponderance of one of the antipodes, the following 

 considerations must be kept in mind. From the standpoint of true catalysis there is no 

 difference in the energy required for the interconversion or the formation of the 1- and 

 d-antipode of a given substance in equal concentrations. Analyzing the principles of 

 the asymmetric synthetic action of enzymes Werner Kuhn (1936) stated that from 

 the thermodynamic point of view the optically active state is not a state of equilibrium 

 as compared with the racemic state. The mixing of the two antipodes to form a race- 

 mate liberates energy, while their separation requires an expenditure of energy. 

 According to Kuhn, in certain instances, the preponderance of optical purity in a 

 system, despite the gradual decrease of optical activity in a single enzymatic process, 

 can be explained by "stereo-autonomic" behavior of some substances. That is, this 

 behavior conditions stable optical purity of the synthetic product. It is knovm that 

 d-mandelonitrile, synthesized by the plant, is stabilized in tlie form of the less soluble 

 and easily crystallizable fi-gentiobioside (natural amygdalin). In contrast the more 

 soluble gentiobioside of 1-mandelonitrile remains in solution. The excess 1-mandelo- 



