KLUYVER S CONTRIBUTIONS TO MICROBIOLOGY AND BIOCHEMISTRY 



peratures that caused protein denaturation had suggested that en- 

 zymes might be proteins or substances associated with proteins, and 

 during the early 'twenties Willstatter and collaborators had assembled 

 a mass of information in support of this view. Finally, in 1926, Sum- 

 ner had announced the isolation of a crystalline protein that pos- 

 sessed the power to hydrolyze urea to ammonium carbonate, thereby 

 establishing that urease, at least, was a typical protein. 



It is understandable that the existence of hydrolytic enzymes had 

 led to the assumption that comparable biological catalysts would be 

 involved in other types of reactions brought about by living organ- 

 isms. And when Buchner had prepared, from ground-up yeast, a cell- 

 free press juice that could still promote a characteristic alcoholic fer- 

 mentation of sugar, this was hailed as proof positive for the enzyme 

 theory of fermentation. Some early successes were booked in preparing 

 from other organisms cell-free juices that caused the formation of lactic 

 acid from sugar, or an oxidation of alcohol or glucose. But the extrac- 

 tion of such enzymes invariably proved more difficult than that of the 

 hydrolases ; it required the use of large quantities of cells, and, be- 

 cause these enzymes were not excreted, they had to be liberated by 

 rupturing the cells. In consequence the composition of these enzyme 

 extracts was exceedingly complex, approximating that of the cells 

 themselves. Now this marked difference in the behaviour of enzymes 

 involved in hydrolyses and in typical dissimilatory reactions, respect- 

 ively, had already been commented on by Kluyver in his 1924 lecture 

 on the 'Unity and Diversity in the Metabolism of Micro-organisms'. 

 Here he had stressed what appeared to him the significant fact that 

 hydrolyses represent preparatory events whereby large, non-diffusible 

 molecules are broken down to small and readily diffusible units, and 

 that, from the point of view of cellular economy, they are devoid of 

 energetic significance. In contrast, the typical dissimilation processes are 

 primarily concerned with energy provision of the cells, which accounted 

 for the fact that the causative enzymes had to be rigorously cell-bound. 



Kluyver was not averse to considering dissimilatory transformations 

 as enzymatic ; in fact, in a series of lectures delivered in Amsterdam 

 in 1929 he had categorically stated: 'Biochemistry in its entirety is 

 enzymatic'. Why, then, did he show so little inclination to include 

 enzymological studies in his programme? There were two different 

 factors to which we can assign an important role. 



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