OPTICAL ACTIVATION 



isomers which, mi account of their /configuration, belong i<> one 

 group. Thus, for example, he has found 1 that d- glucose, 

 d- mannose, d- galactose, and d- fructose all undergo 

 fermentation with yeast, while the laevo isonier- of these sul>- 

 stances do not. Xot only, however, are the micro-organisms 

 ahle to distinguish between isomers of entirely opposed activity, 

 but the transposition of two groups, attached to a single one of 

 a number of asymmetric carbon atoms, is of importance to them. 

 Fischer and Thierf elder 2 have shown that although the above 

 mentioned sugars are fermentable by various yeasts, d- talose, 

 Avhich differs from d- mannose and d- galactose only by the 

 transposition of the groups attached to a single asymmetric 

 carbon atom, is not attacked by the same yeast species. To 

 insure enzyme action, then, the substrate and enzyme must have 

 their configurations adjusted to one another like lock and key: 

 and it may be possible that they may act m one another to their 

 mutual distraction if the keys turn opposite ways. However, 

 experiments made by Eiloart showed 110 such destruction in tin- 

 case of human and pig pepsins. 



The relation between the substrate molecule and that of the 

 enzyme is illustrated 3 by the splitting ,of a - and ft - - methyl 



H C OCH 



H CO C H 



o 



1. Fischer, E.: Zeit. f. physiol. Chem.. 26, 60. (1898). 



2. Fischer. E.. and Thierfelder: Ber. d. deutsch .chem Ges., 27, 2031 

 (1894); see also Fischer, ibid. 27, 2985, 3228, 3479. 



3. Fischer, E.: ibid. 32, 3617, (1899). 



