Activation of sodium cyanide to a toxic but non-mutagenic metabolite in Salmonella typhimurium.

Salmonella typhimurium strains (OASS-positive) synthesize a toxic but non-mutagenic metabolite from cyanide and O-acetylserine. Salmonella typhimurium mutant DW379 (OASS-deficient) is neither able to carry out this reaction in vitro nor produce the toxic metabolite in vivo. L-Cysteine reverses the cyanide metabolite mediated inhibition and thus allows OASS-positive strains to grow in medium containing cyanide and O-acetylserine. The results suggest that the enzyme O-acetylserine sulfhydrylase catalyzes the reaction of cyanide and O-acetylserine to form the toxic metabolite. This metabolite is ninhydrin-positive, adheres strongly to the cation-exchange column, and migrates in TLC to an Rf value similar to that of beta-cyanoalanine.