134 PLANT RESPIRATION 



Lebedew thought that he had found experimentally that 

 di-hydroxy-acetone forms with phosphates the triose-monophos- 

 phate which readily condenses to hexose phosphate. This 

 finding is refuted, however, by more recent studies by Neuberg 

 and his coworkers^ and the Lebedew theory is thereby deprived 

 of its experimental foundation. 



Lebedew- has recently proposed another theory. He sup- 

 poses that the fermentation of sugar beyond the intermediate 

 stages of glyceric aldehyde, glyceric acid and pyruvic acid 

 proceeds of itself. According to v. Lebedew's experiments 

 glyceric acid as well as glyceric aldehyde is fermentable by yeast. 

 Proof of this by no means improbable theory has not yet been 

 worked out. 



Neuberg himself attempts to explain the formation of methyl 

 groups (which will really be the key to the puzzle of alcoholic 

 fermentation) by means of the intermediate formation of methyl 

 glyoxal, and represents the whole process by the following 

 equations in which the Cannizzaro reaction, first proven for 

 yeast by Kostychev,^ plays an important role. 



(I) CeHioOe = C6H804(methyl glyoxal aldol) + 2H2O 



(II) C6Hs04 - 2CH2=COH— CHO or 2CH3— CO— CHO 



Methyl glyoxal 



(III) 2CH2=COH— CHO + 2H0O = 



CH2OH— CHOH— CH2OH + CH3— CO— COOH 



Glycerine Pyruvic acid 



(IV) CH3— CO— COOH = CH3— CHO + CO2 



(V) CH3— CO— CHO -f CH3— CHO = CH3— CO— COOH 4- 



CH3— CH2OH. 



It is evident that such hypothetical equations are noc easily 

 reconciled with the modern conception of the nature of the 

 Cannizzaro reaction. Nor are they very probable on other 

 grounds. For example, the progress of the "mixed" Canniz- 

 zaro reaction (V and III together) and similar problematical 



> Neuberg, C, E. Farber, A. Levite, und E. Schwenk. Biochem. Z. 83: 244. 1917- 



' Lebedew, A. V. Z. f. physiol. Chem. 132 : 275. 1924. 



2 Kostytschew, S. Z. f. physiol. Chem. 89: 367. 191-S 92: 402. 1914. Neuberg's 

 claim (in his latest communication) that he previously succeeded in demonstrating the 

 Cannizzaro reaction with yeast (with reference to Neuberg und Kerb. Biochem. Z. 58: 

 158. 1913) is incorrect. No experimental studies of the Cannizzaro reaction are contained 

 m this communication of Neuberg and Kerb. 



