THE SO-CALLED INORGANIC ENZYMES 227 



colloidal platinum by hydrocyanic acid arises from the same causes 

 as the poisoning of a living cell by that reagent, it is dangerous to 

 apply the same term to both processes. By a strange process of 

 reasoning this same " poisoning " of the colloidal platinum by 

 hydrocyanic acid has been put forward as supporting the view 

 that the platin sol is an " inorganic enzyme." Now, if the process 

 of " poisoning " proves anything at all, it proves that the colloidal 

 platinum is a living cell, for it is living cells and not enzymes that 

 are destroyed by the action of hydrocyanic acid, by which in such 

 minute concentrations most enzymes are entirely unaffected. The 

 only action related to enzymes which is stopped in the same degree 

 by hydrocyanic acid is the identical one to that stopped in the case 

 of colloidal platinum namely, the action upon hydrogen peroxide 

 which is found not only in practically every enzyme but in nearly 

 all tissue extracts. This action is ascribed usually to enzymes 

 called " oxydases " or " peroxydases," occurring generally in all 

 tissues where oxidative processes occur; but our knowledge of the 

 subject is scarcely sufficient to state whether it is to be ascribed to 

 any particular enzyme or group of enzymes, or is a general property 

 attaching to all enzymes. The action, as has been stated, is stopped 

 by a trace of hydrocyanic acid without interfering with the specific 

 action of the enzyme accompanying the " peroxydase "; it is also 

 stopped by the action of heat similarly to that of an enzyme, 

 but it has not clearly been shown that the substance causing the 

 oxidation is not altered in the process, nor that there is no stoichio- 

 metric relationship between the quantity of " peroxydase " and 

 the amount of hydrogen peroxide changed. In fact, it appears that 

 the " peroxydases " are very sensitive, and that after conversion 

 of a certain amount of peroxide the action ceases. 



Whether the " peroxydases " be specific enzymes or not, the 

 action of hydrocyanic acid in stopping or " poisoning," both in 

 their case and that of colloidal platinum, is confined to one re- 

 action, that of the conversion of hydrogen peroxide into water 

 and oxygen, and it appears to the writer that this is a narrow 

 basis on which to lay any weight as a proof of identity in mode 

 of action between enzymes and colloidal platinum. It has not 

 even been proved, for example, that hydrocyanic acid does not act 

 directly as a negative catalyst to the reaction concerned. 



While it cannot be admitted, therefore, that the terms " in- 

 organic enzyme " and " poisoning " can be legitimately employed 



