2IO PHYSIOLOGY OF NUTRITION 



Reductase is plentiful in yeast, and this enzyme has been shown to play an 

 important role in alcoholic fermentation. 1 Palladin and Lvov 2 were able to 

 retard the process of alcoholic fermentation by employing the respiration pig- 

 ment of the white beet to remove the active hydrogen as it was formed. The 

 production of alcohol was thus decreased, as well as that of carbon dioxide. 

 They then employed methylene blue in place of the respiration pigment, and 

 found that for each atom of hydrogen removed by the methylene blue there 

 occurred a decrease of one molecule in the production of alcohol and of carbon 

 dioxide. This dependence of alcoholic fermentation upon reduction processes 

 may be represented by the following simplified scheme, in which M denotes 

 methylene blue. 



2 C 6 Hi 2 6 + M = 2 C0 2 + 2 C 2 H 5 OH + C 6 H 10 O 6 + M-H 2 . 



The methylene blue is reduced to the leuco-compound. In this scheme no ac- 

 count is taken of Palladin's 3 opinion that alcoholic fermentation involves the 

 chemical action of water, nor of Bach's idea that reduction also depends upon 

 such action (see page 228). 



The action of reductase consists in the removal of hydrogen from one sub- 

 stance (de-hydrogenation) and its transmission to another substance (hydro- 

 genation)/ The substance that gives up hydrogen is oxidized and is called 

 the reducer, reductor or reducing agent (R-H 2 ). The other substance, said to 

 be an oxidizer or oxidizing agent, which receives the hydrogen, is called the 

 acceptor of hydrogen (A). The reaction is shown by the general equation, 



R-H 2 + A = R + A-H 2 . 



An example of this is the decomposition of lactic acid by the reductase of yeast, 

 in the presence of methylene blue (M) as a hydrogen acceptor, as shown by the 

 equation: 



CH3-CHOH-COOH (lactic acid) + M = 

 CH3-CO-COOH (pyrotartaric acid) + MH 2 . 



The pyrotartaric acid produced is decomposed by carboxylase, into acetic 

 aldehyde and carbon dioxide. 4 



If it is granted that reduction takes place with the participation of water, 

 then the hydrogen of the water must unite with the acceptor of hydrogen, while 



1 Griiss, J., Untersuchungen liber die Atmung und Atmungsenzyme der Hefe. Zeitsch. ges. Brauwesen 

 27:686-692,699-704,721-724,734-739.752-755.769-772. 1904. Palladin, 1908. [See note i, p. 171.] 



2 Palladin, V. I. (W.), and L'vov, S. D., Sur l'influence des chromogenes respiratoires sur la fermerrtation 

 alcoolique. (Text in Russian.) Bull. Acad. Imp. Sci. St.-Petersbourg VI, 7: 241-252. 1913- Palladin, 

 W., and L'vov, Sergius, Ueber die Einwirkung der Atmungschromogene auf die alkoholische Garung. 

 Zeitsch. Garungsphysiol. 2: 326-337. 1913. 



3 Palladin, V. I. (W.), Sur le r61e des pigments respiratoires dans le respiration des plantes et les ani- 

 maux. (Russian.) Bull. Acad. Imp. Sci. St.-Petersbourg, VI, 6: 437-415. 1912. Palladin, W., Ueber 

 die Bedeutung der Atmungspigmente in den oxydationsprocessen der Pflanzen und Tiere. Zeitsch. Garungs- 

 physiol. 1: 91-105. 1912. 



4 Palladin, Sabanin and Lochinovskaia, Bull. Acad. Imp. Sci. St.-Petersbourg, 1915. P. 701.* 



f This and the four following paragraphs are translated from separate pages in Russian, 

 received from Prof. Palladin. For another statement of these considerations and a report of 

 some later work; see: Palladin, W., and Sabinin, D., The decomposition of lactic acid by killed 

 yeast. Biochem. jour. 10: 183-196. 1916. — Ed. 



