(D) The desuccinylase activity of SIRT5 is stimulated by oxidative stimuli. Flag-SIRT5 was ectopically expressed in HEK293T cells. 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 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 *p<0.05, ***p<0.001 (two-tailed unpaired t-test). 