422 SCIENCE PROGRESS 



hydrolytic reaction may be considered to necessitate a 

 synthesis. 



On further investigation, the hydrolytic and synthetic 

 properties of enzymes are found to be intimately bound up 

 together, indeed they may be considered to proceed syn- 

 chronously in a system, and the equilibrium position may be 

 held to show the rates of the velocity of the hydrolytic to that 

 of the synthetic process. 



For convenience it is perhaps best to group the work done 

 on this subject under the types of substances which are syn- 

 thetised. 



Fats. — Most of the work done to investigate the synthesis 

 of enzymes has been done on fats or fatty acids, as they afford 

 better material for study than carbohydrates or proteins. 

 They are simpler in that they do not form steriosomers and 

 may be used in more concentrated solution. 



Bradley (191 3) concluded from his investigation of fats and 

 lipases in the various tissues of the body that it was very 

 doubtful whether fat was synthetised by enzymes at all ; he 

 found, for example, that the brain contains more lipase than 

 the mammary gland. Such a result is difficult to explain ; but 

 in confirmation of work done prior to the period under review, 

 Armstrong and Gosney (19 14) — as already stated — showed 

 conclusively that lipase does synthetise fats. Further, Hamsik 

 in the same year found that lipase from the intestinal mucous 

 membrane, from the lung, and from the liver could synthetise. 



Proteins. — ^Although it has been realised that a synthesis 

 of proteins necessarily takes place in the building up of tissue, 

 comparatively little work has been done on synthesis by 

 enzymes. This is owing to the difficulty arising from the 

 number of products into which proteins readily break down when 

 hydrolysed. Moreover, since the point of equilibrium in most 

 instances of hydrolysis of protein is close to that of complete 

 hydrolysis, it is obvious that the synthesis can only take place 

 to a very small extent ; and the fact that the enzyme, if not 

 itself a protein, is usually closely associated with protein matter, 

 is an additional difficulty. 



The work of Henriques and Gjaldlec (191 1) established the 

 fact, however, that protein could be synthetised by enzymes. 

 These investigators found that the nearer the substances used 

 were to the products of complete protein hydrolysis the simpler 

 was the substance formed. In this connection it is interesting 

 to note that earlier observers found that the body was quite 

 unable to maintain adequate nitrogen content on food con- 

 sisting of the products of hydrolysis of protein by acid, whereas 

 it flourished on the products of digestion by enzyme. 



Carbohydrates. — Since the earlier work of Croft Hill and 



