BIOGRAPHICAL MEMORANDA 



biocatalysis itself was tackled. Because the essence of every metabolic 

 process appeared to be hydrogen activation, and because Kluyver was 

 prone to search for the ultimate in simplification and generalization, 

 he concluded that one single property might suffice to account for the 

 observed differences in the metabolic behaviour of diverse organisms. 

 The most obvious feature that fulfilled such a requirement was a spe- 

 cific 'affinity' of the protoplasm for hydrogen. 



The idea was developed as follows. A catalysed reaction involves 

 the straining of certain bonds in the molecules of the reacting sub- 

 stances, a 'dislocation', as Boeseken had termed it. Now, differences in 

 the affinity for hydrogen of the protoplasm of different organisms 

 would cause different degrees of such dislocations, which could ex- 

 plain the variety of reactions that substrates and intermediate products 

 can undergo under the influence of diverse organisms. An attractive 

 aspect of this concept was that it eliminated the need to postulate, as 

 was commonly done though without adequate supporting evidence, 

 the occurrence in different cell types of a large number of haphazard- 

 ly distributed enzymes. It was further pointed out that the same de- 

 gree of dislocation in a molecule containing both hydrogen and oxygen 

 atoms can result from a specific activation either of hydrogen or of 

 oxygen, and that a definite affinity for hydrogen is equivalent to a 

 reciprocal one for oxygen. Thus a catalyst with a high affinity for 

 hydrogen possesses ipso facto a low one for oxygen, and vice versa. This 

 also means that a substrate may be dislocated to a comparable extent 

 by catalysts that possess either a high or a low affinity for hydrogen, 

 so that the metabolic processes of characteristically aerobic organisms, 

 representing a high affinity for hydrogen, may come to resemble those 

 of the most anaerobic types, effecting an equivalent substrate activa- 

 tion through their high affinity for oxygen. Indeed, this affinity might 

 even be so great that molecular oxygen would become firmly bound 

 to the catalyst, thereby rendering the latter inactive for further sub- 

 strate activation. This corollary provided a plausible explanation for 

 the deleterious effect of oxygen on obligatory anaerobes. 



It is superfluous to enter here into a detailed discussion of the appli- 

 cation of the principles of hydrogen activation and transfer to a large 

 number of particular metabolic processes ; this can be found in the 

 classical paper by Kluyver and Donker, 'Die Einheit in der Bio- 

 chemie', that has been reprinted in this volume. 



90 



