BIOGRAPHICAL MEMORANDA 



concluding that 'it has become very difficult to deny the enzymatic 

 nature of those dissimilation processes for which the experimental 

 proof is still lacking. For instance, I doubt if anyone would seriously 

 maintain that sugar breakdown by the yeast cell is an enzymatic pro- 

 cess, whereas the analogous fermentation by B. coli has a non-enzyma- 

 tic character' (p. 94) . And what was true for dissimilatory reactions 

 should hold equally for assimilation processes; after all, the synthesis 

 of a new carbon-to-carbon link is encountered also in typical catabolic 

 reactions. Nevertheless, he perceived that this thesis might be less 

 readily accepted, and proceeded to disarm his potential opponents: 

 'But you will perhaps observe that whilst it is easy to ferment sugar with 

 the aid of the enzymes of yeast, it has not as yet been found possible 

 to synthesize fat from sugar with these enzymes, a conversion which is 

 nevertheless of general occurrence in the living yeast cell. However, 

 on second thoughts this is not to be wondered at. For I have only to 

 remind you how the conversion of sugar into fat demands for its 

 successful completion a harmonious succession of a special set of pri- 

 mary reactions out of the many that are possible. And the perfect 

 harmony which is the one condition for such a long chain of reactions 

 is the exclusive prerogative of the living cell' (p. 95). 



Next he considered the implications of the enzymatic interpretation 

 of metabolism: 



'The question then arises whether we have to conclude from the 

 foregoing that a living cell should be considered as an arsenal filled up 

 with enzymes, which successively are brought into action. Such a 

 supposition would only be justified if every chemical reaction brought 

 about by the cell required its own specific catalyst. 



'A survey of modern enzymological literature shows that the doc- 

 trine of the extreme specificity of enzymes is adopted by almost all 

 the leading authorities in this field. . . . All the same, it seems worth 

 while to dwell for a moment on the problem whether this doctrine 

 is actually well founded . . . We should then like to observe in the 

 first place that a catalyst can only be expected to be non-specific, 

 i.e. be able to promote various reactions, in so far as these reac- 

 tions are of the same nature. Now, we have seen that the primary 

 reactions to which biochemistry can be reduced satisfy this demand 

 in a high degree; all these reactions are either of the hydrolytic or 

 of the oxidoreduction type. So at first sight it seems quite conceiv- 



104 



