RELATIONS BETWEEN PROSTHETIC GROUPS, 

 COENZYMES AND ENZYMES 



HUGO THEORELL, Department of Biochemistry, Medical Nobel 



Institute, Stockholm 



The reactions of proteins — most of which seem to be 

 enzymes — are fundamental for biological life, since they play a 

 primary role in both of its essential features : reproduction and 

 metabolism. From a chemical point of view cell division is a 

 complicated and as yet largely unknown chain of reactions be- 

 tween proteins and nucleic acids which occur in cell structures. 

 Metabolism is promoted and governed by a great number of 

 interactions between proteins and their cofactors (for example 

 nucleotides or hematins), and various substrates. 



Whereas the chemical structure of the known prosthetic 

 groups and coenzymes is relatively well established, the structure 

 of proteins is in many respects unknown. Only recently has 

 sufficient progress in protein chemistry been made to permit the 

 hope of being able to find the "active" groups in the proteins, 

 and of formulating in chemical terms what happens when pro- 

 teins react with their cofactors and substrates. We shall discuss 

 here some of the recent results obtained in tliis field, and essen- 

 tially confine ourselves to three oxidation enzymes of different 

 type: cytochrome c, the "old yellow enzyme," and liver alcohol 

 dehydrogenase. 



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