CHEMICAL PHENOMENA IN LIFE 



the chief characteristics of catalytic substances and 

 of enzymes agree exactly. We must in consequence 

 of this consider enzymes to be catalytic agents. 



But there are a few very remarkable and sharp 

 differences between the two groups of substances. 

 Most of the catalysers we have spoken about 

 extend their sphere of action over a large number 

 of substances. Acids, for example, are able to 

 catalyse all kinds of reactions. Quite a different 

 behaviour is met with in enzymes. As a rule 

 enzymes are effective only in one reaction. In- 

 vertin does not act upon anything else but on 

 cane sugar, emulsin only upon amygdalin. Their 

 sphere is, as we see, very limited. Another pecu- 

 liarity of enzymes is their colloidal nature and their 

 inability to resist boiling temperature. There is 

 little doubt that both properties are connected, 

 and that the sensibility to heat is due to coagula- 

 tion of colloidal solutions. We may therefore say 

 that enzymes are catalytic substances of a limited 

 field of action, of colloidal nature, and very little 

 resistent to heat. We must still add that enzymes 

 are formed only in living matter. Finally, one 

 important property of enzymes is this, that in the 

 blood of animals which have had some enzyme 

 solution injected into a vein, peculiar substances 

 are formed. These have the power of hindering 

 the enzyme action when a little of the blood serum 

 is added to a mixture of the original enzyme 

 solution and the substance on which the enzyme 

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