Complex Compounds and Models of Enzymes 



267 



that, in this field, we cannot make further progress towards the synthesis of 

 active structures than the level of activity obtained by using dimethyltrimethyl- 

 enediamine. 



In the work of the American authors to which reference has already been 

 made [7] they did not reach the conclusion that a decrease in the stability of the 

 complexes catalysing hydrolytic processes accompanies an increase in their 

 catalytic activity. 



Maybe the rapid fall in stabiHty as the activity increases in copper models of 

 catalase is one reason why iron plays a more important part than copper in the 

 genesis of biologically active structures acting like catalase, A study (Fig. 3) of the 

 activity of complexes with heterocyclic compounds (pyridine, picoline and 

 piperidine) revealed yet another characteristic feature of catalysts of this type. 



CHp-NH, 



I \ 



CH3-CH-NH2 



CHj— NHj 



CHa— Nl-lj 



CHa-NHj 



CHg-NCCHJj 



50 



100 



150 



Fig. 2. The dependence of a/Al on M for complex compounds of copper with 



different diamines. 



a 

 M 



activity 

 molecular weight. 



A very slight change in the composition of the addendum, e.g. the substitution 

 of pyridine for piperidine, is accompanied by a marked change in activity (the 

 substitution of pyridine for piperidine causes the activity to drop to 1/80 of its 

 former value). This property can also be observed in other classes of complex 

 compounds. Thus, in diamines, the inclusion of a methylene group increases 

 the activity 18 times while methylation of the nitrogen increases it a further 

 10 times. 



Among biologically active substances, such as enzymes, vitamins, hormones 

 etc. this phenomenon of the marked variation of activity is sometimes so strongly 

 pronounced that one can speak of the interdependence of activity and 

 activation. 



