Enzyme Reactions in Stationary Open Systems 



449 



EFG in its transition to a new stationary state GH. Thus at each new accelera- 

 tion of the chemical reaction the system passed over to a new stationary state; 

 in each case it passed through an intermediate extreme position. 



The stationary state of the reaction does not only depend on the rate of the 

 reaction (changing with the addition of an en2yme, cf. Figs. 3-5), or on the 

 original concentration (cf. Fig. 4), but also on the diffusion parameters of the 

 system. 



In the apparatus described above (Fig. 2) we used different membranes with 

 diameters of i-6j 2-4 and 3-7 cm; this corresponds with a change in the area over 

 which diffusion was taking place in the ratio of i : 2-2 : 5-3. In each of these 

 vessels experiments were carried out using a different concentration of enzyme 

 which changed the kinetic parameters of the system in a different way. In this 

 case the curves were similar to those in Figs 3-6, but for each vessel it was 

 found that, at a particular value of K, curves of this first type (Fig. 6, 1) changed 



v_ 







Time, mm 

 Fig. 6. Fundamental types of curves when the stationary state is changed. 



into curves of the second type (Fig. 6, II) in which the new stationary state 

 remains at the lowest level and the concentration does not rise again from the 

 minimima. We shall return to this question later, in our discussion of Table i. 



Finally, in a ntmiber of experiments we studied the effect of altering the rate 

 of the reaction by heating or cooling the system (these experiments were done 

 in vessel II). Heating was not carried above 40°C so that inactivation of the 

 enzyme could be held to be excluded (inactivation of the enzyme by heat was 

 not observed below 8o°C). The first part of the experiment — the establishment 

 of the stationary state without the enzyme and the transition to a new stationary 

 state after the addition of the enzyme — was carried out in just the same way 

 as the preceding experiments. The solution was then heated quickly to 40°C 

 and the temperature was maintained by the passage of nmning water, heated to 

 42°C which bathed the outside of the membrane for 60 min. As may be seen 

 from Fig. 7 (curve I) the system had not yet attained a stationary state by the 

 end of that time (third type of curve. Fig. 6, III). However, when heated to 

 30°C the system still attained the stationary state although in this case the 

 minimum was shallow (Fig. 7, curve II). On the other hand, when the system 



29 



