Sod1 integrates oxygen availability to redox regulate NADPH production and the thiol redoxome.

Cu/Zn superoxide dismutase (Sod1) is a highly conserved and abundant antioxidant enzyme that detoxifies superoxide (O 2 •- ) by catalyzing its conversion to dioxygen (O 2 ) and hydrogen peroxide (H 2 O 2 ). Using Saccharomyces cerevisiae and mammalian cells, we discovered that a major aspect of the antioxidant function of Sod1 is to integrate O 2 availability to promote NADPH production. The mechanism involves Sod1-derived H 2 O 2 oxidatively inactivating the glycolytic enzyme, GAPDH, which in turn reroutes carbohydrate flux to the oxidative phase of the pentose phosphate pathway (oxPPP) to generate NADPH. The aerobic oxidation of GAPDH is dependent on and rate-limited by Sod1. Thus, Sod1 senses O 2 via O 2 •- to balance glycolytic and oxPPP flux, through control of GAPDH activity, for adaptation to life in air. Importantly, this mechanism for Sod1 antioxidant activity requires the bulk of cellular Sod1, unlike for its role in protection against O 2 •- toxicity, which only requires <1% of total Sod1. Using mass spectrometry, we identified proteome-wide targets of Sod1-dependent redox signaling, including numerous metabolic enzymes. Altogether, Sod1-derived H 2 O 2 is important for antioxidant defense and a master regulator of metabolism and the thiol redoxome.