450 A. G. PASYNSKIÏ 



Addition of enzyme 

 I 

 . ._, , ^ Heating to 40 



* I '^ i 



L • — •— •— I — • — •— •— •— *^^ 



\ 



E 



i 



^ 61- 



Addition of enzyme ^^^^.^ ^^ 30° 



V.-—- * — • — .—-.-.-, — 



Addition of enzyme ^^^ij^g ^o 15° ,^*^*-'''' 



.. 1 . U-" 



^^ 



J I I I L 



J I 1 I L 



040 60 80 100 120 140 160 180 200 220 240 260 280 300 



Time, min 



FiG. 7. Enzymic oxidation of ascorbic acid under flowing conditions at 

 différent temperatures. 



was cooled to I5°C and the reaction became slower, a reverse began to take 

 place in the course of the process (Fig. 7, curve III). In this case also, the 

 stationary state of the system was not reached after two hours. Similar results 

 were obtained from experiments in which the heating and cooling of the system 

 was carried out in the absence of the enzyme. Thus, in experiments in cyHnder 

 II, the stationary state of the system was shown to be limited by changes in 

 temperature over a range of only a few degrees. 



DISCUSSION OF RESULTS 



The enzymic oxidation of ascorbic acid under flowing conditions is one of the 

 simplest examples of an open enzymic system. It differs from the systems in 

 enclosed vessels which are usually studied, by the existence of a constant con- 

 nection with a surrounding medium, both in respect of receiving reacting sub- 

 stances from the environment and in respect of casting out the products of the 

 reaction into it. From the evidence which has been adduced it is clear that, even 

 in its simplest form, such a system has new, distinctive properties which are 

 absent from an enclosed system — in the first place there is the development of a 

 state which remains stationary over an unlimited period of time. This is based 

 on the continual renewal of the composition of the system and a dynamic balance 

 of the processes of inflow and outflow. From equation (2) it may be seen that the 

 estabhshment of this state depends on a particular relationship between the 

 kinetic and diff"usional parameters of the system and the initial concentration of 

 the components. If any one of these parameters is changed, the system passes 

 from one stationary state to another. In fact, it may be seen from the curves in 

 Figs. 3-7 that an open system has considerable adaptability in respect of altera- 

 tions in the rate of reaction (brought about, in our experiments, by changes in the 

 amount of enzyme, heating or cooling the system, repeated addition of enzyme 

 and combination of the effects of enzyme and temperature), to alteration in 



