Purification of a fluoroacetate-specific defluorinase from mouse liver cytosol

Fluoroacetate-specific defluorinase, an enzyme which catalyzes the release of fluoride ion from the rodenticide fluoroacetate, has been purified 347-fold from mouse liver cytosol and shown to be distinct from multiple cationic and anionic glutathione S-transferase isozymes. Fluoroacetate-specific defluorinase was obtained at a final specific activity of 659 nmol of F^-/min/mg of protein and was prepared in an overall yield of 12%. The isoelectric point of this hepatic enzyme was acidic, at pH 6.4, as determined by column chromatofocusing. The molecular weight of the active species was estimated at 41,000, and sodium dodecyl sulfate-polyacrylamide gels of the purified defluorinase demonstrated a predominant subunit, M(r) = 27,000. Chromatofocusing completely partitioned the fluoroacetate-specific defluorinase from two separate peaks of murine anionic glutathione S-transferase activity. Rabbit antibodies prepared against the purified hepatic defluorinase quantitatively precipitated native defluorinase from mouse and rat liver, but were unable to immunoprecipitate cationic or anionic glutathione S-transferase enzymes from the same preparation. The evidence presented suggests that fluoroacetate-specific defluorinase and glutathione S-transferase activities are catalyzed by separate proteins present in the cytosol of mouse liver.