20 



1. Deamination or reduction plays an important part in the 

 formation of ammonium salts in the soil. The amino group is 

 .split off as ammonia and non-nitrogenous organic acids remain. 

 It is not certain whether this process involves oxidation of the 

 amino acid to the ketonic acid first, or whether the deamination is 

 brought about by hydrolysis. If the hydroxy acids are first formed 

 they are subsequently reduced so that the fatty acids are formed 

 from the amino acids. This can be illustrated by the following 

 examples : 



Aspartic acid will give succinic acid, and this by loss of carbon 

 dioxide gives propionic acid. 



Tyrosine >p-Hydroxy-phenyl-propionic acid >p-Hydroxy-phenyl-acetic 

 acid >p-Cresol > Phenol 



This deamination or reduction is in all probability what is 

 termed in soil chemistry ammonification. 



2. Decarboxylation or amine formation involves the splitting 

 off of carbon dioxide by the action of so-called carboxylase bac- 

 teria. This may happen either before or after deamination. Their 

 formation is illustrated in the following reactions: 



CH 3 -CH(NH,)-COOH- >CH :r -CH,.-NH,.+ CO 2 

 Alanine Ethyl amine 



C, i H 4 (OH)-CH 2 -CH(NH 2 )-COOH - ->CoH 4 (OH)-CH 2 -CHo-NH 2 +CO 2 

 Tyrosine p-Hydroxy-phenyl-ethyl amine 



>NH 2 -CH 2 -CH :! -CH 2 -CH ; -NH 2 +CO 2 

 Lysine Cadaverine 



NH 2 -C(NH)-NHCH 2 -(CH 2 )r-CH(NH 2 )-COOH- 



Arginine NH 2 -C(NH)-NH-CH 2 -(CH 2 ) 2 -CH 2 -NH 2 +CO 2 



Agmatine 



Tryptophane gives rise to indole ethyl amine. 

 Mathews (1915) states 



If the splitting: off of carbon dioxide occurs after the deamidization an amine 

 cannot, of course, be formed, but the next lower carboxylic acid is produced 

 by way of the aldehyde. 



Thus from tyrosine there may first be formed p-hydroxy- 

 phenyl-pyruvic acid, which may be reduced to p-hydroxy-phenyl- 

 lactic acid, reabsorbed and reexcreted in the urine ; or the p-hy- 

 droxy-phenyl-pyruvic acid may be split into p-hydroxy-phenyl 

 acetaldehyde and carbon dioxide, and the former be oxidized into 

 p-hydroxy-phenyl-acetic acid, which is excreted in the urine. 



It is well to remember that any bacteria of the coli group will 

 split off carbon dioxide from an amino acid. It is evident that 

 mixed cultures of bacteria may be present in the soil and thus cause 

 more than one type of splitting to take place. 



3. Hydrolysis takes place with liberation of carbon dioxide 

 Ehrlich (1911) has shown that yeasts can convert amino acids into 

 alcohols, liberating carbon dioxide and ammonia. 



C 6 H4(OH)-CH 2 -CH(NH 2 )-COOH + H 2 O -- > 



Tyrosine CoH 4 (OH)-CH 2 -C 



Tyrosol 



