ENZYME ACTION 51 



c;ieniical reactions; ami 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 rapid that the 

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

 substances the reaction is very slow, and without the presence of 

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

 ample, ethyl butj'rate saponifies on the addition of water according 

 to the following equation: 



C.H5 - O - OC - C3H7 + H2O ^ C0H5OH + HOOC - C3H7. 



On the other hand, if ethjd alcohol and butj-ric acid, the products 

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

 butyrate; in other words, the reaction is reversible, as indicated by 

 the arrows in the equation. In any event, however, the reaction is not 

 complete, but continues only until there exists a certain definite pro- 

 portion of ethyl alcohol, butyric acid, eth3'l butyrate, and water, when 

 the change will stop, i. e., equilibrium is established. The time that 

 would be required for this reaction to occur at room temperature 

 would be extremely long, the change being hardly noticeable, but in 

 the presence of a catalytic agent the reaction goes on much more 

 rapidly. Catalytic agents, therefore, merely hasten reactions which 

 would go on without them, and they do not initiate or change the na- 

 ture of chemical reactions at all. When equilibrium is established, the 

 reaction stops and the enzyme has nothing more to do. Furthermore, 

 enzj^mes will hasten synthesis just as well as they hasten catalysis. 

 Croft Hill first showed that maltase would synthesize glucose intc 

 maltose; Kastle and Loevenhart soon after estabhshed the synthesis 

 of ethyl butyrate under the influence of lipase. Taylor^ ° first syn- 

 thesized one of the normal body fats, triolein, by the action of hpase 

 (from the castor-oil bean) upon oleic acid and glycerol. Successful 

 synthesis of fats by pancreatic lipase is described by Lombroso.^^ 

 It may seem improbable at first sight that the synthesis of proteins 

 can be accomplished by enzymes, as is the relatively very simple 

 synthesis of carbohydrates and fats, but the improbability disappears 

 when we recall that the products of protein cleavage are reconverted 

 into body proteins after absorption from the intestines. Proteins 

 manifestly are synthesized and we have not a little reason to believe 



9 See Taylor, Arch. Int. Med., 190S (2), 148. 

 i» Univ. of California Publications (Pathology), 1904 (1), 33. 

 11 .\rch. di farmacol., 1912 (14), 429. 



