Enzymic Reactions in Stationary Open Systems 445 



where the boundaries of the system are indicated by the dotted lines, 5" and Z 

 refer to the external medium and K and K' are the velocity constants of the 

 forward and backward chemical reactions A ^ D. If the processes of transfer 

 take place according to Pick's law and the chemical reaction follows an equation 

 of the first order, then if the stationary concentration of substance A is dyna- 

 mically maintained constant at a, then, by the method of Burton and Denbigh 

 [6, 7] we obtain the equation 



Ko(K'+K^)S+K'K^ . . 



a = — ^ — ^ (l) 



KqKz + KqK' + KKz 



In the conditions of the experiments which I am about to describe the transfer 

 of substance D took place in pure running water (Z == 0), furthermore, for an 

 irreversible reaction such as the oxidation of ascorbic acid by hydrogen peroxide, 

 K' = o. In this case equation (i) is greatly simplified and becomes: 



(2) 



1 + ^ 



Ko 



From equation (2) one may see that the value of a depends on the concentra- 

 tion of the source S, the constant of transfer Ko and the velocity constant of 

 the chemical reaction K. A change in any one of these parameters of the open 

 system, or in the external conditions (temperature, pressure etc.) will cause the 

 concentration of ascorbic acid to find a new stationary state. 



From the general theory of open systems [5] there emerge the following 

 characteristic properties of the stationary state which are of interest in con- 

 nection with our present work: In an open system catalysts (enzymes) affect 

 not only the rate of the reaction, but also the stationary concentration of the 

 reacting substances. If the conditions of the stationary state in an open system 

 are changed, compensatory processes develop which tend to conserve the 

 properties of the system; this is an extension of Le Chatelier's principle (the 

 dynamic stabilization of the stationary state). The transition from one stationary 

 state to another in an open system does not follow a imiform curve but passes 

 through extreme states (usually through maximal or minimal states). 



In the Uterature, these properties have been investigated on hydrodynamic 

 models with rtmning water [6] and in the reaction of persulphuric acid with 

 glucose [7]. As we have already mentioned, the present investigations were 

 for the first time carried out on an enzymic reaction (the oxidation of ascorbic 

 acid). 



EXPERIMENTAL SECTION 



The ascorbic acid was crystalline. The hydrogen peroxide was chemically 

 pure (28%). The peroxidase was isolated from horse radish, the preparation 

 having an activity of about 35% on the purpurogallin scale. The concentration 

 of ascorbic acid in the mixture was o-6%, and that of hydrogen peroxide o-i%, 

 i.e. the molar concentration of ascorbic acid was rather higher (by 15%). 1-3 mg 



