Complex Compounds and Models 

 of Enzymes 



L. A. NIKOLAEV 



Department of Chemistry, Moscow Institute of Transport Engineers 



The progress which has been attained in enzymology during the last decade is, 

 to a considerable extent, attributable to the use of the model method. Since the 

 time of the well known experiments of Bredig [i], in which he compared the 

 catalytic powers of metallic salts with the properties of enzymes, and those of 

 Warburg [2] which were concerned with studying the so-called 'charcoal models', 

 studies have been made of model systems more similar to enzymes in their 

 chemical nature. 



The classical investigations of W. Langenbeck and also the recent work of 

 Lautsch are typical in this respect [3, 4]. 



Langenbeck's fundamental idea was that one may approach an understanding 

 of the chemical nature of enzymes by gradually increasing the complexity and 

 changing the structure of such organic molecules as have, in some degree, the 

 same catalytic properties as the enzyme. The brilliant success of Langenbeck's 

 own work has shown that this method is essentially correct. 



Langenbeck's models (e.g. the well known models of carboxylases and esterases) 

 have been incomparably more helpful towards such an understanding than those 

 in which the properties of organic substances were simulated by metals. 



This certainly does not mean that one should regard 'metallic' models as 

 being of no significance. They are systems in which the action of electronic 

 mechanisms can be observed more directly than in complicated biocatalysts and 

 a consideration of the part played by these mechanisms in biochemistry certainly 

 acted as a stimulus. 



However, the physical chemistry of complicated structures can obviously not 

 be simply deduced from the properties of structures of a simpler type; many 

 important regularities which are clearly expressed in highly organized systems 

 are scarcely to be observed in simple molecules. 



In the present paper we shall describe models of active groups of enzymes 

 containing metals, we shall consider their thermodynamic properties and the 

 question of adsorptive activation and, finally, we shall turn to models which do 

 not contain metals. 



As models of active groups we have chosen various complex compounds of 

 the transition metals which have catalytic properties exactly suited to carrying 

 out the processes brought about by catalases and oxidases. 



As addenda in the complexes studied we used hydroxy acids, amino acids, 



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