226 THE SO-CALLED INORGANIC ENZYMES 



to this certain of the differences in action between inorganic 

 catalysts and enzymes are due. 



The method of Bredig for obtaining, in the case of certain 

 metals, catalysts of inorganic nature in colloidal solution as metal 

 sols is hence of high interest. These metal sols have been termed 

 inorganic enzymes by Bredig from their close resemblance in many 

 respects to the enzymes produced by living cells ; but it is question- 

 able whether the use of such a term is justifiable, since the properties 

 of such colloidal solutions are only exaggerations, probably on 

 account of increased surface, of the action of the finely divided 

 metals when not in solution, and most of the reactions destroying 

 or removing the properties of such solutions may be ascribed to 

 the throwing of the metal out of solution or to alteration of the 

 active surface. 



We have no proof that the similar actions in the case of the 

 enzymes are due to similar causes. Also, we have no case where 

 these colloids act upon another colloid as in the case of enzymes, 

 nor of any hydrolytic action upon organic bodies caused by their 

 agency as in the case of enzymes. In fact, their action is con- 

 fined to simple reactions upon inorganic bodies, such as the cata- 

 lysis of hydrogen peroxide into water and oxygen, or .of hydrogen 

 and oxygen to form water. Such reactions are shown by the metals 

 concerned in finely divided form apart from solution, and the 

 increased activity is merely due to finer division, and is removed 

 by anything which interferes with the action of the large surface. 

 Accordingly, it appears to the writer that the term " inorganic 

 enzyme " is not a very appropriate name for a colloidal solution 

 of platinum, since it indicates that we possess more knowledge of 

 the mode of action of enzymes than we really do. 1 The same 

 applies to the term " poisoning " as supplied to the action of 

 hydrocyanic acid and sulphuretted hydrogen in stopping the action 

 of such metal sols when added in minute traces, for this term is 

 one which has hitherto been applied to the destruction of life by 

 reagents, and until we know that the stopping of the action of 



1 The suggestion of Oppenheimer (Die Fermente, p. 46), that it would be 

 better to call the enzymes " organic catalysts," is much better if any change 

 must be made. For it is much better to retain the name catalyst as a general 

 class name, including both inorganic and organic, and the enzymes now form 

 a well-defined group of organic catalysts for which the name ought to be 

 retained. 



