218 BACTERIOLOGICAL CHEMISTRY 



and vice versa. The toxicity of isoleiic'me, CH.NH2.COOH, 



CH 



CH3 CHgCHg 



norleucine, CH.NHa.COOH, 



CH 



H CHo.CIlq 



or serine, CH.NH2.COOH, 



CH 



H OH 



is removed by a mixture of valine and leucine but not 

 by either alone. The toxicity of serine can be removed 

 by threonine. Definite quantitative relationships between 

 the amounts of the amino-acids exist but they are not 

 necessarily equimolecular. 



The amino-acids are less readily utilised by 

 yeasts than are ammonium salts, which stimulate 

 their utilisation. The amino group of asparagine, 

 COOH.CH.CH2.CONH2, is utilised more readily than 



NH2 



the amide group. 



It is possible that the breakdown of certain amino- 

 acids serves as the energy source for the anaerobes CI. 

 sporogenes and CI. hotulinum. The reaction, described 

 by Stickland, is between two amino-acids, one activated 

 as hydrogen acceptor and the other as donator ; glycine, 

 Z-proline and Z-hydroxyproline are acceptors, and Meucine, 

 c?-alanine, f/- valine, /-phenylalanine, i-aspartic acid and 

 rf-glutamic acid serve as donators. Tlie reaction is 

 probably according to the equation : — 



KiCH.NHo.COOlI. HiCO.COOH 



+ " r H2O — > + 1 2NH3 



RCH.NHo.COOH 



