kluyver's contributions to microbiology and biochemistry 



instances of hydrogen transfer mechanisms ; and even the condensa- 

 tion reactions appeared amenable to the same interpretation. 



This general theme was developed in more detail in a later pub- 

 lication by Kluyver and Donker in which an array of arguments was 

 presented to show how this concept of hydrogen transfer as the funda- 

 mental feature of all metabolic processes could lead to yet further 

 simplification and unification. Here it was also pointed out that, 

 examined from this viewpoint, the apparently fundamental difference 

 between fermentative and oxidative metabolic processes disappeared, 

 and that the latter should be regarded as special cases of regeneration 

 of protoplasm from its hydrogenated state through the transfer of the 

 excess hydrogen to molecular oxygen. And the next step resulted in 

 a simple and appealing synthesis of the conflicting ideas on biological 

 oxidations that had been developed by Wieland and by Warburg, 

 respectively. As mentioned, the former had interpreted biological 

 oxidations as representing primarily instances of activation of sub- 

 strate-hydrogen by biological catalysts, and had shown that they may 

 proceed in the absence of oxygen provided a suitable alternative hy- 

 drogen acceptor be present. Conversely, Warburg had long empha- 

 sized the drastic inhibitory effects of substances such as cyanide, car- 

 bon monoxide, and hydrogen sulphide on biological oxidations, and 

 defended the thesis that these effects were compatible with the inact- 

 ivation of iron-containing catalysts whose mode of action was con- 

 cerned with the activation of molecular oxygen. Kluyver and Donker 

 now showed that the presumably incompatible theories of Wieland 

 and Warburg were complementary, and, in fact, were both needed 

 to explain the dual aspects of the mechanism of biological oxidations 

 which should involve, at one end, an activation of substrate-hydrogen 

 (Wieland's postulate), and, at the other, activation of molecular oxy- 

 gen (Warburg's theory) . Almost simultaneously, and quite independ- 

 ently, von Szent Gyorgyi in studies with plants, and Fleisch in studies 

 with animals, had advanced the same idea. Nevertheless, it may here 

 be stressed that Kluyver and Donker had arrived at the most general 

 formulation in demonstrating that the Wielandian principle can be 

 used for the interpretation not only of biological oxidations, but of 

 any and all metabolic phenomena, whereas the Warburg principle is 

 applicable only in those cases where oxygen is the final oxidant. 



Once this universal synthesis had been achieved, the problem of 



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