io6 



R. MAMELAK, J. H. QUASTEL 



VOL. 12 (1953) 



RESULTS 



Competition of amino acids for a common reduction mechanism 



Initial experiments were carried out to discover whether all the amino acid hydrogen^ 

 acceptors are activated by the same enzyme or whether they are involved in a common 

 reduction mechanism in CI. sporogenes. Results given in Table I show that varying the 

 concentration of L-proline from 0.005 ^'^ to 0.04 M has little or no effect on the speed 

 of alanine-proline interaction, indicating saturation of the proline reductase at these 

 concentrations. Similarly, it will be seen that in the alanine-glycine interaction, glycine 

 reductase is saturated with its substrate at 0.02 M to 0.04 M. On adding a mixture of 

 proline and glycine at these concentrations to alanine, an additive effect on the speed of 

 carbon dioxide evolution is not observed, as would be the case if completely separate 

 mechanisms were involved. The rate of formation of ammonia in the alanine-proline 

 interaction is increased to a small extent by the addition of glycine, but a summation 

 of effects is not demonstrable. If smaller concentrations of proline and glycine than those 

 quoted are used, additive effects may be found, but it is easily shown that these are due 

 to the fact that the proline becomes rapidly reduced, after which further glycine 

 utilisation takes place. The results indicate that proline and glycine compete either for a 

 common enzyme or for a common factor involved in the reduction of the amino-acids. 



TABLE I 



ALANINE-GLYCINE-PROLINE INTERACTIONS IN PRESENCE OF CI. SpOVOgeneS 



Mixtures of alanine and glycine, alanine and proline, or alanine, glycine and proline were 

 incubated for various intervals of time with i ml freshly prepared CI. sporogenes suspension made 

 up in 0.15 M KCl in Warburg manometer vessels in 0.028 M NaHCOg. Temp. 37°. Gas 93% Ng 

 -f 7% COg. Total vol. 3.2 ml. Alanine placed in side tube and tipped at commencement of expt. 



Results obtained with lyophilised CI. sporogenes show that the proline and glycine 

 reductases are distinct from each other. With such a preparation, it is found that the 

 rate of alanine-glycine interaction is negligible whilst that of alanine-proline proceeds 

 rapidly. 



It is, therefore, apparent that proline and glycine must normally compete, in intact 

 CI. sporogenes, for a common factor, possibly a hydrogen carrier, involved in their 

 reduction. 



Ferricyanide as a hydrogen acceptor ivith CI. sporogenes 



Typical results shown in Table II make it clear that ferricyanide is reduced by a 

 variety of amino acids in presence of resting CI. sporogenes. The amino acids that 



References p. 120. 



