(F) Chemical oxidants enhance the ability of SIRT5 to activate IDH2. Flag-SIRT5 was ectopically expressed in HEK293T cells, and the transfected cells were treated with increased concentrations of Paraquat or H2O2 for the indicated periods. Flag-SIRT5 was purified by immunoprecipitation with Flag beads, eluted with Flag peptide, and then incubated with purified Flag-IDH2 in vitro. IDH2 enzyme activity was measured as described in 'Materials and Methods', normalized by its protein level. The results are average ± SD of 3 independent experiments **p<0.01, ***p<0.001 (two-tailed unpaired t-test). 