ANTI-FERMENT REACTION 361 



From experimental evidence, Czapek considers that the 

 first alternative is the true one. He found reason to believe 

 that the inhibiting substance is an anti-oxidase of some po- 

 tency which is precipitated by alcohol, destroyed by heat (62°) 

 and may be isolated by filtration through a porcelain candle. 

 Czapek further ascertained that the anti-oxidase is more or 

 less specific, for although the oxidase and the anti-oxidase of 

 closely related plants have a mutual action, this is not so for 

 plants widely separated. 



It is supposed that the anti-oxidase is only produced as a 

 result of gravitation stimulus, so that the simple reaction is as 

 follows. The tyrosine is converted by the action of tyrosinase 

 into homogentisinic acid ; the further oxidation of the acid by 

 oxidase is inhibited by the production of an anti-oxidase which 

 renders the oxidase more or less inefficient, and so the homo- 

 gentisinic acid accumulates. 



For the mode of quantitatively determining the amount 

 of homogentisinic acid and for other details, Czapek's paper 

 must be consulted. 



The interaction between enzyme and antienzyme appears 

 to be of the nature of adsorption. 



ENZYMES AND THE LAWS OF MASS ACTION. 



According to the Law of Mass Action enunciated by 

 Guldberg and Waage, the rate at which a body undergoes 

 chemical change is dependent on the concentration as 

 measured by the number of gram molecules of substance 

 present in the litre ; consequently the amount of substance 

 changed in unit time will be greater at the beginning of the 

 reaction than towards the end, since the amount of un- 

 changed substance is continually decreasing. 



The relationship between the amount of substance x 

 (measured in gram molecules per litre) changed in time t 

 (measured in minutes) and the original concentration a of the 

 substance is given by the equation : — 



The above formula holds only for the decomposition of a 

 single substance, and it is, therefore, characteristic of what is 

 known as a Monomolecular reaction or a reaction of the first 



