Effect of Nitrofurans on the Respiration of E. coli. III

Inhibitory Effect on the Oxidation of TCA Cycle Members

Abstract

Oxidation of pyruvic, oxalacetic, and acetic acids by the live bacterial suspension of Escherichia coli is not inhibited under the conditions by which malic acid oxidation is partially (25%) inhibited. Even under the same conditions, preincubation of the bacterial suspension with Furacin to effect complete inhibition of malic acid oxidation results in the inhibition of the oxidation of pyruvic, oxalacetic, and acetic acids. However, oxidation of succinic and formic acids, even after such preincubation, showed the absorption of oxygen corresponding to 1 atom of oxygen per mole of substrate, indicating that the one-step reaction of succinic to fumaric acid and formic acid to carbon dioxide still remains. The concentration for 50% inhibition, I₅₀, of nitrofurans against malic oxidation by bacterial suspension were: 2-(5-nitro) furfural semicarbazone 10^-4 M; 5-nitrofurylacrylamide, 3×10^-5M; 5-nitrofurfural aminoguanidine, 3×10^-5 M. The succinic oxidase obtained by extraction after exposure of E. coli to supersonic waves was not inhibited by 5×10^-4 M of 5-nitrofurfural semicarbazone.