14 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



cases the chemical action is probably resolvable ultimately 

 into similar factors, though the nature of the products and 

 the energy or heat changes are different in the two cases. 



A simple case which illustrates the difference between 

 what may be termed digestive and respiratory fermentation 

 is afforded by the decomposition of urea in the presence of 

 micro-organisms. The simple fermentative change consists 

 in the transformation of the urea into ammonium carbonate 

 by the addition of a molecule of water, as in the following 

 equation : 



CO(NH 2 ) 2 + 2H 2 = (NH 4 ) 2 C0 3 



At the same time a portion of the nitrogen is found to be 

 taken up by the organism with simultaneous production of 

 C0 2 . The second is a much more complex change than the 

 first and its conditions are not so fully understood, but it 

 is probable that here also we have to do with a chemical change 

 in which intermediate loosely compounded complexes are 

 formed, as in the simpler purely chemical reactions mentioned 

 in the earlier part of the chapter. 



Finally, it has been found possible, as already stated, not 

 only to break down substances in the manner indicated 

 through the agency of enzymes, but also to effect syntheses 

 of more complex from less complex compounds. Thus, e.g., 

 Croft Hill has been able to produce isomaltose by the action 

 of the enzyme maltase upon dextrose, as follows : 



2C 6 H 12 6 H 2 = C 12 H 22 O n 



This discovery is of very far reaching importance and 

 opens up a wide field of possibilities. Already Emil Fischer 

 and his co-workers have announced the synthesis of certain 

 decomposition products of albumin by means of enzyme action. 



In the following pages the attempt will be made, by means 

 of typical examples, to render clear the methods of investiga- 

 tion which are used in the study of the chemistry of changes 



