kluyver's contributions to microbiology and biochemistry 



FURTHER DEVELOPMENTS: PHOSPHORYLATION AND 

 THE NATURE OF ASSIMILATION 



The successes scored in interpreting the vast diversity of metabolic 

 processes in a simple and unified manner understandably induced a 

 desire more rigorously to test the applicability of the principles to spe- 

 cific cases. Among the first to be so investigated was the mechanism 

 of alcoholic fermentation. In part this may have been owing to Kluy- 

 ver's earlier preoccupation with this fermentation ; but in part it must 

 also be ascribed to the recognition that an as yet mysterious and un- 

 explained phenomenon had been observed in this fermentation. The 

 concept of hydrogen transfer had already made it possible to integrate 

 the carbinol condensation and the phytochemical reductions with the 

 more normal reactions. And the one aspect that had so far remained 

 outside the scope of speculations now promised to shed some further 

 light on the introductory conversion of a fermentable hexose molecule 

 into the postulated two triose molecules. 



For nearly twenty years it had been known that the fermentation of 

 sugar by yeast press juice or maceration juice is accompanied by the 

 intermediate formation of hexose phosphate esters, and on the basis 

 of quantitative experiments Harden and Young had established a rela- 

 tionship between the formation of carbon dioxide and alcohol on the 

 one hand, and of hexose phosphate on the other, that could be ex- 

 pressed by the equation: 



2 C 6 H 12 6 -2H 3 P0 4 -> G 6 H 10 O 4 (PO 4 H 2 ) 2 +2H 2 O+2GO 2 +2C 2 H 5 OH 



However familiar we may be with the current interpretation and sig- 

 nificance of this equation, it should be remembered that in the 'twen- 

 ties it did no more than paraphrase an over-all result, and that, taken 

 at face value, it might suggest that concomitantly with the esterifica- 

 tion of one sugar molecule another one was broken down to carbon 

 dioxide and alcohol; a rational interpretation had not been suggested. 

 It is equally significant to realize that during the early 'twenties 

 great strides had been made in our understanding of the structure of 

 sugars; Haworth, Irvine, and their collaborators had established the 

 ring structure of hexoses. It was this aspect that caused Kluyver to 

 look for a potential connexion between the act of phosphorylation and 

 the subsequent rupture of a hexose molecule into two triose moieties 



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