Pnc1p supports increases in cellular NAD(H) levels in response to internal or external oxidative stress

Following transfer from medium with fermentable glucose to medium with nonfermentable acetate as the carbon source, cellular levels of NAD(H) were found to increase ∼2-fold in a parental yeast strain. Similar transfer of a mutant strain subject to endogenous oxidative stress under these conditions produced more dramatic increases in cellular levels of NAD(H), and elevations above parental levels were shown to be due to the nicotinimidase Pnc1p. Similar transient increases in NAD(H) levels observed in the parental strain following addition of exogenous hydrogen peroxide were also attributable to Pnc1p.