160 BREAKDOWN OF NITROGENOUS MATERIAL 



Oxidative deamination 



Oxidative removal of the — NHg group is accomplished 

 according to the equation 



R.CHNH2.COOH + > K.CO.COOH + NH3, 



with the production of the a-keto-acid corresponding to the 

 amino-acid attacked. This is the type of breakdown found 

 in mammalian kidney cells, but whereas most amino-acids 

 are attacked by oxidative deamination in these tissues, in 

 bacteria this method of attack is restricted to certain organisms 

 and specific amino-acids. Esch. coli is known to deaminate 

 glycine, L-alanine and l -glutamic acid in this way with the 

 formation of glyoxylic, pyruvic, and a-ketoglutaric acids 

 respectively. 



H2NCH2 . COOH -f > CHO . COOH + NH3 



CH3 . CHNH2 . COOH -f > CH3 . CO . COOH + NH3 



HOOC.CH2.CH2.CHNH2.COOH + 



^^ HOOC . CH2 . CH2 . CO . COOH + NH3. 



In the case of glutamic acid the reaction is really accomplished 

 in two stages, in which the first stage consists of a dehydro- 

 genation to imino-glutaric acid, which is then spontaneously 

 hydrolysed to ketoglutaric acid. 



COOH COOH COOH 



I I I . 



CH2 CH2 CH2 



I Glutamic I I 



CH2 - 2H ^— ^ CH2 -f H2O ^^ CH2 + NH3 

 I dehydrogenase I I 



CHNH2 C-NH C = 



I I I 



COOH COOH COOH 



This deamination process is essentially similar to that 

 which occurs in mammalian tissues, with the difference that 

 whereas liver L-glutamic acid dehydrogenase requires 

 coenzyme I, the enzyme of Esch. coli requires coenzyme II. 



