E. J. Russell and E. H. Richards 523 



than indicate the leading lines. The first stages in the bacterial decom- 

 position break the protein down to amino-acids ; the change seems 

 to be identical with the ordinary laboratory decomposition brought 

 about by sulphuric" acid and other hydrolysing agents. 



The special feature of bacterial decomposition is that these amino- 

 acids break down still further, and the change may go on in two 

 directions : 



1. Deaminisation, i.e. the elimination of ammonia. This is a very 

 common change and is produced under both aerobic and anaerobic 

 conditions ; indeed it is not solely a bacterial process, but seems to be 

 a widespread property of the living celU. We are here concerned only 

 with deaminisation by bacteria, a subject which has been much in- 

 vestigated 2. Of the aerobic processes known to bring it about two 

 have been described by Dakin^: 



R . CH . NH2 . COOH + O, = R . COOH + CO, + NH3 



R . CH . NHo . COOH + H2O = R . CH . OH . COOH + NH3 



whilst another which, so far as is known, is confined to yeast, was 

 discovered by Ehrlich*: 



R . CH . NH2 . COOH + H2O = R . CH2OH + CO2 + NH3 . 



Besides these there are the following anaerobic processes, one 

 accompanied by reduction : 



R R 



CHNH2 + 2H = CH2 + NH3 

 COOH COOH 



and another recently studied by Raistrick^ in which there is no 

 reduction : 



R . CH2 . CHNH, . COOH -^ R . CH : CH . COOH +NH3. 



1 See "The Physiology of Protein Metabolism," Cathcart, Longman'' s Biochemical 

 Monographs, 1912, pp. 49-55. 



2 E.g. Brasch and Neuberg, Biochem. Zeit. 1908, 13, 299 ; and 1909, 22, 403. Neuberg. 

 ibid. 1909, 18, 424 et seq. and 1909, 20, 450 et seq. Borchardt, Zeit. f. physiol. Chem. 

 1909, 59, 96. 



3 Dakin, J. Biol. Chem. 1908, 4, 63. 



* Ehrlich, Zeitsch. Verein Biibenzucker Inch 1905, 539-67. 

 5 Biochem. J. 1917, 11, 71. 



