56 EXZYMEfi 



certain relation of jreometrieal stnicture between an enzyme and the 

 substances it acts upon, and leaves little question of its material na- 

 ture. 



Bredif? has found that colloidal sohifio)is of metals have many of 

 the properties of true enzymes, aeeomi)lishino- many of the decom- 

 positions produced by enzymes, being affected by temperatures of 

 nearly the same degree, and even being ''poisoned" by substances 

 that destroy or check enzymes. The only possible explanation of these 

 observations seems to ])e that the enzyme effects are brought about by 

 surface phenomena. A colloidal solution of platinum, so far as is 

 known, differs from a piece of metallic platinum solely in the enor- 

 mously great amount of surface it offers in proportion to its weiglit, 

 and it is well known that surfaces may affect chemical action. 

 Hence we have the possibility that some enzyme actions, at least, 

 may depend upon the existence of a very large surface, and since 

 by no means all colloids are enzymes, that this surface must bear a 

 certain relation in form to the surface of the body that is to be acted 

 upon. 



THE PRINCIPLES OF ENZYME ACTION 



The effects produced by enzymes, which at one time were con- 

 sidered ciuite unique and remarkable, have now been made compara- 

 tively plain, chiefly through the observations of Ostwald on related 

 chemical reactions ; and by the investigations of Croft Hill, Kastle 

 and Loevenhart, and others, on enzymes, which show that enzyme 

 action is in no way different from chemical action observed independ- 

 ent of enzymes. The fundamental consideration is that chemical re- 

 actions are reversible, that is, that their tendency is to establish an 

 equilibrium, and that the change may be from either side of the equa- 

 tion.^ The action of enzymes is similar to that of all catalytic agents, 

 that is, they increase the speed of reaction. In the case of such a 

 reaction as that of NaOH and HCl, the reaction is so ra])id that the 

 effect of catalyzers could hardly be noticed ; but with many other 

 substances the reaction is very slow, and without the ])resence of 

 catalyzers it would go on almost or quite imperceptibly. For ex- 

 ample, ethyl butyrate saponifies on the addition of water according 

 to the following equation : 



CJI— 0— OC— CJI: -f- R,O^CJI,OH + IIOOC— C,H;. 



On the other hand, if ethyl alcohol aiid butyric acid, the products 

 of this reaction, are placed together, they will combine to form ethyl 

 butyrate; in otlier words, the reaction is rexci-sible, as indicated by 

 the arrows in the e(|uation. In any event, however, the reaction is not 

 complete, but continues only until a certain deHnite pro})ortion of 



5 See Taylor, Arcli. Jut. ^\vd., IJIOS (2), 14S 



