314 Professor William J, Pope [May 1, 



in the buildiDg up of very complex molecules from simpler ones, such 

 for instance, as the formation of starch from carbon dioxide and 

 water. A specific case in which enzymic action leads to the pro- 

 duction of a complex substance from simpler ones has been recently 

 worked out by Fischer and Armstrong, who show that the enzyme, 

 lactase, converts the sugar galactose, C6H12O6, into a new sugar, iso- 

 lactose, Ci2H220ii, of nearly twice the molecular weight of the former. 

 All the enzymes with which we are acquainted appear to be 

 enantiomorphous bodies ; they are perhaps substances to which no 

 definite molecular composition can ever be assigned, inasmuch as 

 they may be systems consisting of a number of different true chemical 

 compounds, the system being one which becomes endowed with 

 extraordinary chemical activity when placed in a suitable environ- 

 ment. The enantiomorphism of the enzymes has been repeatedly 

 demonstrated during the course of Emil Fischer's remarkable 

 synthetic work on the sugars. Fischer succeeded in preparing fruit 

 sugar by purely synthetical methods as a mixture of the dextro- and 

 the laBvo-isomerides ; in order to isolate the previously unknown 

 1-fructose he applied the third Pasteur method in that he cultivated 

 a yeast in the solution ot the compensated fructose. The yeast 

 enzyme — presumably zymase — has arrived at its present stage of 

 development by passing through countless generations, all of which 

 have been fed upon sugars of the dextro-configuration, these being 

 the only ones occurring in nature. In Fischer's experiment, the 

 enzyme therefore readily devoured the d-fructose but refused to 

 touch the 1-fructose, which had never before been presented to it. 

 The 1-fructose was of course subsequently isolated from the solution. 

 The need for compatibility between the enzyme and the material 

 upon which it has to act is very elegantly illustrated by considering 

 the efi'ect of yeast upon a number of optically active and isomeric 

 sugars. In the table are given the constitutions of a number of 

 sugars of the composition CgHioOg, the configurations of the three or 

 four asymmetric carbon atoms present in the molecule being indicated 

 by writing the hydrogen atoms on the right or the left of the figure, 

 as the case may be. 



COH CH2OH COH COH COH 



The beer yeast ferments d-glucose, d-manncse and d-fructose, 

 each of which contains a similar set of three asymmetric carbon atoms 



