ENZYMES 183 



to a key and the substance split up to a lock, is a very happy one. 

 The simile can be extended still further, since the key may unlock 

 thousands of similar locks and fails only when the key is worn out. 

 Moreover, only very small quantities of enzymes are needed which 

 are utilized over and over again. This conception of enzymes corre- 

 sponds with our present-day chemical conception of catalyzers. These 

 latter are substances which either bring about or accelerate chemical 

 reactions, without themselves figuring in the end products. For in- 

 stance, platinum hastens the combination of O and SO 2 into 80s, or 

 the union of H 2 and into H 2 O. 



It is the nature of catalyzers that they split up compound sub- 

 stances and build up the same substances from the cleavage products 

 until a definite equilibrium is obtained. Thus, ricin, the enzyme of 

 the castor bean, not only splits fat into glycerin and fatty acid but 

 also unites glycerin and fatty acids into fats. The equilibrium is 

 frequently one in which the synthetic action seems very subordinate. 

 Thus, amylase under certain circumstances splits up 99 per cent 

 of starch, yet it forms possibly but 1 per cent of starch from maltose. 

 This, being a colloid, precipitates from the solution, and thus permits 

 the formation of another 1 per cent of starch which gradually ap- 

 pears as starch grains or glycogen and thus permits the further for- 

 mation of starch. ; 



Hitherto, it has been impossible to obtain an enzyme in pure form 

 and only by its stronger or weaker activity was it known whether a 

 dilute or a concentrated preparation of enzyme existed. W. M. 

 BAYLISS rightly calls attention to the fact that, on account of their 

 colloidal nature, enzymes always carry down by adsorption portions 

 of the solutions from which they are obtained. It is, therefore, not 

 surprising that albumin reactions are obtained from pepsin and tryp- 

 sin and a carbohydrate reaction from amylase and invertase. In 

 many cases it is possible to decide by means of diffusion whether 

 mixtures are present (see R. O. HERZOG and KASARNOWSKI*). Ac- 

 cording to L. ROSENTHALER,* the presence of albuminous substances 

 is of biological importance, protecting the enzyme from many de- 

 structive influences, especially from H and OH ions. As the result 

 of the constant presence of adsorbed impurities, we know almost 

 nothing concerning the chemical nature of enzymes. However, we 

 do know that all enzymes are colloids. 



S. FRANKEL assumes that pure diastase is very greatly dispersed 

 but as yet no sufficient evidence has been adduced; neither observa- 

 tion in the ultramicroscope nor filtration through a 4 per cent ultra- 

 filter is conclusive. To us it merely seems probable that such 

 diastase is more highly dispersed than hemoglobin. 



