12 NITROGEN METABOLISM 



but nothing is known about the properties of the enzyme 

 concerned. 



Glutamic acid dehydrogenase 



The deamination of glutamic acid by Esch. coli is due to 

 the enzyme L-glutamic acid dehydrogenase with the co- 

 enzyme triphosphopyridine nucleotide (TPN) [2]: the end- 

 product is a-ketoglutaric acid and it is believed that the 

 reduction takes place in two stages: 



COOH.(CH2)2CH(NH2)COOH+TPN+ ^ 



COOH.(CH2)2C(:NH)COOH+TPN.H+H+ 



COOH.(CH2)2C(:NH)COOH+H20 ^ 



COOH.(CH2)2COCOOH+NH3 



The system is reversible, with the equilibrium in favour of 

 the synthesis of glutamic acid. A similar specific glutamic 

 dehydrogenase occurs in Saccharomyces cerevisiae [i], 

 Clostridium sporogenes [44], N. crassa [23], and probably 

 in Haemophilus pertussis [34] and H. parainfluenzae [36]. 

 Haemophilus influenzae will not grow except in the presence 

 of a porphyrin (the X-factor) and diphosphopyridine 

 nucleotide (DPN), TPN or nicotinamide riboside (the 

 V- factor). The oxidative activity of cells harvested from a 

 medium deficient in the V-factor was considerably increased 

 by the addition of DPN or TPN, and in this way Klein 

 has shown that the latter are involved in the oxidation 

 of aspartic and glutamic acids to CO 2 , NH3 and acetic 

 acid [36]. Unlike H. parainfluenzae, no volatile fatty acid 

 was formed during the oxidation of amino-acids by H. 

 pertussis, an organism which requires neither X nor V fac- 

 tors, and in the experimental conditions employed by Jebb 

 and Tomlinson, only carbon from glutamic acid was incor- 

 porated into cell substance [34]. 



Oxidation of tryptophan by Pseudomonas spp. 



A characteristic feature of species of Pseudomonas is that 

 they possess or quickly acquire the ability to utilize any one 

 of a wide variety of oxidizable organic substances as sources 



