KLUYVER S CONTRIBUTIONS TO MICROBIOLOGY AND BIOCHEMISTRY 



possible types of hydrogen transfer reactions in their most generalized 

 form, as: 



(i) AH+B->A-fBH; 



(2) AH-B->A-BH; 



(3) AH-B-^ A+BH; and 



(4) AH+B^A-BH 



And here, finally, Kluyver developed his matured version of the con- 

 cept that there is no need to assume a fundamental difference between 

 those aspects of metabolism that had been so carefully differentiated 

 in the 1924 lecture, viz., catabolism and anabolism. 



To be sure, the nature of assimilatory processes had already been 

 discussed by Kluyver and Donker in 1926, in Part VI of 'Die Einheit 

 in der Biochemie', where it had been stated that the principle of hy- 

 drogen transfer can adequately account also for the synthesis of the 

 major cell constituents, the carbohydrates, fats, and proteins, from the 

 substrate molecules. The same theme was treated more fully in the 

 paper Kluyver [1930] contributed to the first volume of the newly 

 established 'Archiv fur Mikrobiologie', on the interrelations between 

 fermentation, oxidation, and assimilation. Now no longer pre-occu- 

 pied with the problem of how to conceive of an energetic coupling of 

 assimilatory and dissimilatory processes that did not have one or more 

 components in common, Kluyver here reasoned that dissimilation 

 should be considered as the means whereby, through oxidation-re- 

 duction reactions, molecular entities are produced that have a higher 

 energetic potential than the substrate itself. The formation of acetal- 

 dehyde during the degradation of sugar was used as an example; 

 through aldol condensations, dehydrations, and reductions, this sub- 

 stance could be converted into fatty acids in a manner fully compat- 

 ible with mechanisms encountered in the spontaneously occurring 

 catabolic reactions. Since the formation of glycerol from sugar, as, 

 for example, in yeast fermentation, is also part of a typical catabolic 

 process, the synthesis of fat from sugar could be understood as the 

 result of a sequence of step reactions none of which involved prin- 

 ciples different from those used in explaining the spontaneous, energy 

 liberating catabolic conversions. It had therefore become superfluous, 

 and even appeared ill-advised, to postulate that biosyntheses cannot pro- 

 ceed without a special influx of energy; rather should one interpret the 



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