AMINO ACIDS 451 



Baly and his co-workers * claim to have synthesised 

 a-amino acids by exposing an aqueous solution of form- 

 hydroxamic acid and formaldehyde to ultraviolet light. 



From the plant physiological point of view, however, the 

 interest of these latter discoveries is dependent on the occur- 

 rence in the plant both of unsaturated acids and of ammonia. 



The researches of Ehrlich f upon the action of yeast on 

 amino acids showed that the addition of leucine or isoleucine to 

 a fermenting sugar solution gave rise to the production of 

 inactive or active amyl alcohol respectively, according to the 

 following schemes : — 



CHaX CH3\ 



^CHCH^CHNH^COOH + H,0 = ^CHCH^CHoOH + CO2 + NH3 



CH3/ CH3/ 



Leucine Amyl alcohol 



)CHCH20H + CO2 + NH3 



C2H5/ C2H5 



Isoleucine Active amyl alcohol 



The amounts of these alcohols produced are proportional 

 to the quantities of leucine or isoleucine added and rose, under 

 favourable conditions, to as much as 7 per cent ; furthermore, 

 it was found that although the leucine parted with its 

 nitrogen in the form of ammonia, the latter substance was not 

 lost, but appeared to be taken up by the yeast in the produc- 

 tion of new protein material ; this observation led to trying 

 the effect of adding ammonium salts, when it was found that 

 the yeast, finding these latter to be an easier source of 

 nitrogenous food, gave up attacking the leucine, and conse- 

 quently less amyl alcohol was produced. 



These experiments, therefore, prove that amino acids can 

 be fermented by yeast with the production of alcohols in 

 much the same way as sugars can be fermented. The amino 

 acids of the protein of the yeast cells are the source of the amyl 

 alcohol and succinic acid found among the products of the fer- 

 mentative activity of such living yeast cells. When yeast 

 juice is employed, these bye-products are not formed. The 

 practical importance of these discoveries can be gauged from 



* Baly, Heilbron, and Hudson, "J. Chem. Soc," 1922, 121, 1078. 

 t Ehrlich : " Ueber die Bedeutung des Eiweisstoffwechsels, etc.," 

 " Sammlung chem. u. chem. tech. Vortrage," Stuttgart, 191 1. 



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