Studies on the Action of Sulfonamides on the Respiration and Growth of Bacteria

Abstract

Sulfathiazole and Na pyruvate compete for the active site of carboxylase. Presence or absence of inhibition depends on which of the 2 substances gets to the active site of the enzyme first. Para-aminobenzoic acid failed to reverse the strong inhibition exercised by acetaldehyde on carboxylase. In contrast, it reversed the inhibition exercised by sulfathiazole on the carboxylase activities of Escherichia coli and Staphylococcus aureus. In expts. on the inhibition of growth and carboxylase activities of E. coli and S. aureus, practically the same number of sulfathiazole molecules were found to be neutralized by one molecule of p-aminobenzoic acid. The sulfonamide-antagonizing property of p-aminobenzoic acid has been shown to compare with the protective action of other well-known enzyme inhibitors. From the standpoint of the criteria of catalysis, p-aminobenzoic acid.behaves like an inhibitor of catalysis, and not like a catalyst.