PFOR activities upon no treatment.

N = 3 biological replicates.I. PFOR in vivo inactivation and in vitro reactivation after treatment of amoebae with SNP. Trophozoites were incubated for 30 or 60 min in culture medium in the absence or presence of SNP. Clarified extracts were prepared under anaerobic conditions and PFOR activity (in U/mg protein) was then determined. PFOR in vitro reactivation was performed in extracts of SNP-treated amoebas by incubating with DTT and Fe2+ for 1 or 2 h.II. PFOR in vitro inactivation by SNP. Soluble fractions from control amoebae were prepared under anaerobic conditions. Aliquots were incubated in the presence of SNP and in the absence or presence of PTIO for 20 min; the remaining PFOR activity was determined as the ratio of the results obtained for the tested condition and for untreated extracts. Two independent amoeba extracts were assayed, both with control PFOR activities of 1.2 U/mg cellular protein.