Complex Compounds and Models of Enzymes 271 



is different, in principle, from that of simple ions and also, like the activity of 

 enzymes, it is based on the formation of intermediate products. 



Let us now turn to a consideration of the thermodynamic peculiarities of 

 catalysis by complexes. 



In our laboratory A. P. Sychev, R. D. Korpusova, V. V. Yushina and I 

 imdertook the measurement of the energy of activation of various reactions 

 catalysed by model compoimds. We found that, in the case of the catalase reac- 

 tion, the energy of activation in the presence of the catalyst was almost the same 

 as the energy of activation of the thermal decomposition of hydrogen peroxide 

 (cf. Table 3). 



Table 3 



Energy of activation of the reaction of decomposition of hydrogen peroxide 

 catalysed by complex compounds of copper 



It follows that, in this case, the acceleration of the reaction is of purely entropie 

 origin. L. S. Kitsenko and I obtained a similar result in a study of the catalytic 

 activity of the manganese ion in the oxidation of indigo carmine by hydrogen 

 peroxide. 



Models of oxidases present a more complicated picture. R, D. Korpusova and 

 I have studied the oxidation of pyrogallol by oxygen catalysed by copper com- 

 plexes and found that the complex compounds had an effect on the entropy 

 factor and on the energy of activation of the oxidative reaction [18]. The well- 

 known formula of the theory of the transitional state : 



mX = lne. — -\- -^ — ^r^ 

 h R RT 



enables us to derive an expression for the rate of change of entropy in the cata- 

 lysed and imcatalysed reaction in the form: 



A5^ = the entropy of activation for the catalysed reaction 

 A5^= „ „ „ „ „ „ uncatalysed „ 



According to the nature of the addendum the difference A5 — ASo may 

 vary not only in magnitude but in sign, i.e. the catalyst may give rise to a tran- 



