344 ENZYMES 



the formation of some sort of compound between the enzyme 

 and the substrate. 



It should, however, be noted that the action of enzymes is 

 not entirely specific, inasmuch as the one and the same enzyme 

 may be able to hydrolyse two or more substances. Thus mal- 

 tase is able to hydrolyse both maltose and a methyl glucoside ; 

 and emulsin is able to decompose yS methyl glucoside, /S 

 methyl galactoside, milk sugar, amygdalin (the glucoside of 

 bitter almonds, and with which it is primarily associated in 

 nature), arbutin, salicin, and coniferin. 



The specific nature of the interaction between enzymes and 

 other substances is, however, only really strongly marked in 

 connexion with optically active substances. For, taking the 

 case of the fat-splitting enzymes or lipases, practically all esters 

 are broken up by pancreatic lipase, although the ease with 

 which the hydrolysis is effected may vary considerably in dif- 

 ferent cases. 



On the other hand, Fischer and Abderhalden have shown 

 that whereas pancreas extract was able to hydrolyse a num- 

 ber of artificial polypeptides, it was quite unable to act upon 

 others. 



Fischer has described enzymes as optically active cata- 

 lysers, and explains in this way how it is that they produce 

 optically active substances from inactive material, as, for ex- 

 ample, when moulds, such as Penicilliiim glaucuni, Aspergillus 

 niger, etc., are allowed to grow upon inactive tartaric acid with 

 the formation of 1-tartaric acid ; it is assumed that the enzymes 

 combine with the racemic substrate to form isomeric substances 

 which decompose at different rates and so form optically active 

 products. 



A most important contribution to the elucidation of the 

 activity of enzymes is the discovery of the stimulating or in- 

 hibiting influence exercised by certain substances which may 

 be described respectively as Activators and Paralysers. 



ACTIVATORS. 



Under this heading are included substances described by 

 different authors as Co-enzymes * or Accelerators. In some 



* Bayliss distinguishes between co-enzymes and accelerators by reserving 

 the former term for those substances without which the enzyme is unable to 



