KLUYVER S CONTRIBUTIONS TO MICROBIOLOGY AND BIOCHEMISTRY 



chemists, notably Meyerhof and von Euler, were already engaged in 

 studying the nature of this material. 



Now, the theory of alcoholic fermentation that Kluyver and Struyk 

 had developed called for the participation of two different kinds of 

 catalysts, viz., a phosphorylating and an hydrogen activating agent. 

 Besides these nothing else should be needed with the possible excep- 

 tion of a substance that could serve as the initial hydrogen acceptor 

 for the conversion of methyl glyoxal into pyruvic acid. According to 

 the theory, acetaldehyde should be suitable for this purpose, and 

 Meyerhof, in fact, had already shown that a dialysed yeast juice could 

 sometimes be reactivated by the addition of trace amounts of this 

 substance. Meyerhof had also found that the fermentation induced by 

 a zymase preparation was frequently accelerated by small amounts of 

 hexose diphosphate. This, too, could be explained within the frame- 

 work of Kluyver and Struyk's theory by assuming that the phosphor- 

 ylation would proceed more effectively with the hexose ester than 

 with inorganic phosphate. 



So far the experimental results did not present serious obstacles to 

 a simple explanation of the co-zymase effect. But it had also been 

 established that zymase preparations, after ultrafiltration and pro- 

 longed washing, yielded an inactive residue that could no longer be 

 reactivated by hexose phosphate and acetaldehyde, although boiled 

 yeast extract or the concentrated dialysate did restore the activity. 

 Thus the problem was raised how this presumably more genuine co- 

 zymase effect could be explained. Kluyver believed that the answer 

 would be found in earlier studies of Buchner, Haehn, and others, who 

 had postulated that the decline in fermenting capacity of a yeast juice 

 was due to a decomposition of the zymase itself by proteolytic enzymes 

 present in the original juice. This hypothesis could easily be elaborated 

 to explain the reactivation of a zymase residue; it was but necessary to 

 assume that the boiled yeast extract could in some manner protect 

 the zymase against proteolytic degeneration. 



Numerous preliminary experiments seemed to support this expla- 

 nation. Nevertheless, the reactivation of a thoroughly washed ultra- 

 filtration residue was always accomplished by the addition of materials 

 that could not be guaranteed to have been entirely devoid of co- 

 zymase. And a crucial experiment that could serve to abolish the 

 notion that an additional and functionally mysterious factor was need- 



