3 1 8 Biological Chemistry. 



do not definitely decide the question of the stages through 

 which dextrose passes when it undergoes the ordinary 

 process of yeast fermentation. Enough has been said, 

 however, to indicate the value of researches of this descrip- 

 tion, for it is not at all improbable that dextrose undergoes 

 in the body of higher animals changes similar to those 

 produced in yeast fermentation. One investigator, in fact, 

 claims to have isolated ethyl alcohol from mammalian blood 

 and tissue, although this statement has not been confirmed 

 by later investigators. 



Another interesting observation on yeast fermentation 

 may be quoted here. Felix Ehrlich has shown that the 

 amyl alcohols of fusel oil formed as by-products in alcoholic 

 fermentation owe their origin, not to the sugar, but to the 

 leucine and isoleucine derived from the hydrolysis of the 

 proteins present in the fermenting liquor. The reactions 

 can be represented by the following equations : 



(1) (CH 3 .) 2 CH-CH 2 CH(NH 2 )-COOH + H 2 



Leucine. 



= (CH 3 ) 2 -CH.CH 2 -CH 2 (OH) + C0 2 + NH 3 

 Isoamyl Alcohol. 



(2) CH 3 CH(C 2 H 5 ) CH(NH 2 ) COOH + H 2 



Isoleucine. 



= CH 3 CH(C 2 H 5 ) CHS- OH + C0 2 + NH 3 

 c?-Amyl Alcohol. 



Other amino-acids can be degraded in the same way. 

 The method of experiment consisted in the addition of 

 various amino-acids to sterile sugar solutions and fermenta- 

 tion under aseptic conditions with pure cultures of yeast. 

 The higher alcohols produced under these conditions were 

 isolated, identified, and estimated. The amounts of higher 

 alcohols obtained corresponded closely with the amount 

 and character of the amino-acid present. It is not unlikely 

 that amino-acids undergo a similar deaminization in the 



O 



bodies of higher animals, 





