FIGURE 2.

SIRT3 promotes ROS defense systems. SIRT3 deacetylates and activates MnSOD and IDH2, increasing their activity. MnSOD scavenges superoxide produced by the respiratory complexes, converting it to hydrogen peroxide which is further converted to water. Activation of IDH2 by SIRT3 increases its activity, thus producing more NADPH for use by glutathione reductase. GR converts oxidized glutathione to its reduced form, which is further used by GPX to convert the reactive hydrogen peroxide into water. O₂, molecular oxygen; ${\mathrm{O}}_{\mathrm{2}}^{\mathrm{•}\mathrm{-}}$, superoxide; MnSOD, manganese superoxide dismutase; H₂O₂, hydrogen peroxide; CAT, catalase; GPX, glutathione peroxidase; GSH, reduced glutathione; GSSG, oxidized glutathione; GR, glutathione reductase; NADP⁺, nicotinamide adenine dinucleotide phosphate; NADPH, reduced nicotinamide adenine dinucleotide phosphate; IDH2, isocitrate dehydrogenase 2.