I08 R. MAMELAK, J. H. QUASTEL VOL. 12 (1953) 



The addition of alanine to a hydrogen-glycme, or a hydrogen-proline, interaction 

 completely suppresses hydrogen utilisation. The ammonia formation in alanine-glycine, 

 or alanine-proline interaction in presence of hydrogen is practically identical with that 

 obtained anaerobically in the absence of hydrogen (Table III). 



Thus it is evident that hydrogen and amino acid hydrogen donators compete for a 

 common mechanism involved in amino acid reductions in CI. sporogenes. 



The enzyme activating molecular hydrogen (hydrogenase) is not that concerned 

 with the activation of alanine as hydrogen donator, for it may be shown that extracts of 

 CI. sporogenes that bring about amino acid interaction have no hydrogenase activity. 



It must be concluded, therefore, that the suppression of hydrogen utilisation in the 

 presence of alanine cannot be due to competition for a common enzyme and must 

 therefore be due to competition for a common factor (presumably a hydrogen carrier) 

 involved in the amino acid interactions. 



Diphosphopyridine nucleotide (DPN), as a hydrogen carrier, in amino acid interactions in 

 CI. sporogenes 



The addition of DPN to a cell free extract of CI. sporogenes markedly stimulates 

 amino acid interactions. Typical results with alanine-proline and leucine-proline are 

 shown in Table IV. Similar results are obtained with leucine-ornithine, alanine-ornithine 

 and serine. Such a stimulation is not seen with intact resting CI. sporogenes. 



TABLE IV 



EFFECT OF DIPHOSPHOPYRIDINE NUCLEOTIDE (dPN) ON AMINO ACID INTERACTIONS 

 IN CELL FREE EXTRACTS OF CI. SpOVOgeueS 



Amino acids (0.02 M L-form) placed in Warburg manometer vessels in 0.028 M NaHCOg in 

 presence of 93 % Ng -f 7 % COg and i ml cell free extract of CI. sporogenes in i % sodium thio- 

 glycollate solution and 0.002 M phosphate. Nicotinamide present 5.0 mg. Total volume 3.2 ml. 

 Temp 37°. Time 120'. Alanine placed in side tube and tipped at commencement of expt. 



The results with DPN make it evident that this substance plays an intermediary 

 role in amino acid interactions. Moreover the facts that have been recorded concerning 

 the competition of amino acid hydrogen acceptors and of ferricyanide for a common 

 factor are all consistent with the view that DPN is the factor involved. It has been long 

 known (Quastel and Wheatley'^^) that ferricyanide is an oxidant of DPN linked 

 dehydrogenase systems. It follows, too, from these observations that amino acid hydrogen 

 donators, as well as molecular hydrogen, compete for the reduction of DPN. That alanine 

 can accomplish this process is already clear from the evidence of Nisman and Mager^"*. 



These conclusions, indicating the course of events in CI. sporogenes, may be ex- 

 pressed as follows : 



Amino Acid + DPN + H.,0 ^ Corresponding + NH3 + DPNH, 



Hydrogen Donator " a-Ketonic Acid 



References p. 120. 



