Notably, H2O2 induces loss of viability in YPH250 cells with ~7U of catalase activity per mg protein which, significantly, is also abserve for wild-type BY4741 cells. In this strain the maximum stimulated catalase activity is close to10U per mg protein and cell become sensitive to H2O2 at 0.4mM. Interestingly, both stains require ~10U of catalase activity per mg protein for protection against a bolus of H2O2 in the low millimolar range and, in the absence of catalase stimulation, the observed viability drops below 25℅.