The metabolism of phenylalanine and leucine by a cell suspension of Eubacterium brachy and the effects of metronidazole on metabolism.

Degradation of phenylalanine and leucine by resting cells of Eubacterium brachy ATCC 33089 were studied under strict anaerobic conditions. The effects of metronidazole and air on the metabolism were also studied. The organism principally produced phenylpropionate and isocaproate from phenylalanine and leucine, respectively. Other products were cinnamate and phenylacetate from phenylalanine, and alpha-ketoisocaproate and isovalerate from leucine. The organism also produced hydroxylated end-products, i.e. phenyllactate from phenylalanine and hydroxyisocaproate from leucine. When metronidazole was added to the reaction mixture, the production of phenylpropionate, cinnamate, phenylacetate, isocaproate, alpha-ketoisocaproate and isovalerate was inhibited, while that of hydroxylated products was not, suggesting that the organism has metronidazole-sensitive and -tolerant pathways of metabolism. A similar inhibitory effect was also found when the reaction was done aerobically, suggesting that the inhibitory mode of metronidazole is similar to that of oxygen.