BIOGRAPHICAL MEMORANDA 

 COMPARATIVE BIOCHEMISTRY 



The concept of the 'unity in biochemistry' evolved from the idea that 

 all metabolic processes can be interpreted as sequences of step reac- 

 tions, each one representing an intra- or intermolecular transfer of 

 hydrogen under the influence of cellular catalysts. During its develop- 

 ment several types of sugar fermentations had been analyzed in some 

 detail, and it had been found that all of these could be explained as the 

 end result of an identical primary conversion, leading through hexose 

 monophosphate to methyl glyoxal, with modifications arising only in 

 the fate of the latter compound (See, e.g., Kluyver's review [1935]). It 

 has already been mentioned that, by changing the environmental 

 conditions during the fermentation, the intermediate products derived 

 from methyl glyoxal could be diverted into channels that were more 

 or less abnormal for the particular organism ; the formation of acetyl 

 methyl carbinol by yeast and lactic acid bacteria in media with added 

 hydrogen acceptors is a good case in point. Later Kluyver and Molt 

 [1939] showed that B. coli can also be induced to form this substance 

 in trace amounts. 



Of even greater significance was the application of the theory to the 

 fermentations of substances other than the common hexoses. An ex- 

 cellent example is furnished by the studies of Braak [1928Tb] in Kluy- 

 ver's laboratory on the fermentation of glycerol ; they established that 

 the anaerobic decomposition of the polyalcohol by members of the 

 coli-aerogenes group of bacteria may follow one of two distinct pat- 

 terns. The first yields products that qualitatively and quantitatively 

 resemble those of a sugar fermentation by the same organism; this 

 type of fermentation is characteristic for strains that can decompose 

 glycerol only in the presence of an additional hydrogen acceptor with 

 which glycerol can first be converted into a triose, the latter being the 

 genuine fermentable substrate. The second is encountered in those 

 cases where glycerol can be fermented in the absence of an additional 

 acceptor ; these fermentations are characterized by the appearance of 

 trimethylene glycol (1,3-propane diol) as a fermentation end product 

 in an amount roughly equal to one-half of the glycerol fermented, the 

 other half being recoverable in the form of products typical of a normal 

 sugar fermentation. Such results could easily be understood by as- 

 suming an initial conversion of glycerol in which one molecule of the 



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