Thus, starvation prevents induction of Ctt1 activity by attenuating de novo Ctt1 synthesis and/or by promoting NADPH depletion rates following the YPD-KPi switch may contribute to the relatively large variation in catalase activity of unchallenged cells in KPi. Nevertheless, all three strains exhibit comparable H2O2 hypersensitivity in KPi and the protective effect of Ctt1 activity seen in YPD is obliterated on nutrient withdrawal.