OXIDATIVE DEAMINATION 161 



Both stages of the reaction are reversible so that L-glutamic 

 acid can be synthesised from ammonia and a-ketoglutaric acid. 

 This may represent the main path of glutamic acid synthesis 

 in bacteria. In mammalian tissues, the glutamic acid dehydro- 

 genase may act as a carrier system for the deamination (or, in 

 reverse, the synthesis) of other amino-acids, as some workers 

 claim that transamination occurs between either a-keto- 

 glutaric acid and any other amino-acid or, alternatively, 

 between glutamic acid and any other a-keto-acid. This may 

 not be the case in bacteria, as so far it has not been possible 

 to demonstrate transamination other than in a very restricted 

 sense in these organisms (see p. 94), and there is definite 

 evidence, on the other hand, that the deamination of some 

 amino-acids passes through reactions quite different from those 

 involved in the postulated glutamic acid carrier system of 

 mammalian tissues. 



Esch. coll would seem to attack the three amino-acids 

 mentioned by oxidative deamination, but no others. Stumpf 

 and Green have, however, recently found an L-amino-acid 

 oxidase in Pr. vulgaris, Ps. pyocyanea, and Aerobacter aerogenes, 

 which attacks 11 amino-acids: the laevo-isomeis of phenyl- 

 alanine, tyrosine, leucine, iso-leucine, methionine, tryptophan, 

 histidine, norleucine, norvaline, amino-butyric acid, and 

 arginine. In each case the corresponding ke to-acid is formed 

 according to the equation 



R . CHNH2 . COOH + > E . CO . COOH -f NH3. 



The enzyme has been isolated in a cell-free state by disin- 

 tegrating a thick suspension of the bacteria wdth supersonic 

 vibrations. Other common naturally-occurring amino-acids 

 are not attacked in the presence of the enzyme, although the 

 intact organism is capable of a wider range of deaminating 

 activities and must consequently possess other enzymes 

 affecting the deamination of these other amino-acids. The 

 enzyme cannot be obtained from Esch. coli, S. haemolyticus, 

 B. suhtilis, or Staph, aureus. The suggestion is made that 

 there are several bacterial amino-acid oxidases, and that the 

 specificity of these enzymes varies with their source. 



CHEM. A. B. 11 



