(E) In vitro incubation with chemical oxidants does not affect the desuccinylase activity of SIRT5. Flag-tagged SIRT5 was ectopically expressed in HEK293T cells, and then purified by immunoprecipitation with Flag-beads and eluted with Flag peptide. The purified Flag-SIRT5 was treated with increased concentrations of Paraquat or H2O2 at room temperature for 1 hr, and then subjected to the desuccinylase activity assay as described in 'Materials and Methods'. The SIRT5 desuccinylase activity was normalized against its protein level. The results are average ± SD of 3 independent experiments. n.s.: not significant (two-tailed unpaired t-test). 