Comparison of Yarrowia lipolytica and Pichia pastoris Responses to Oxidative Stress Induced by Hydrogen Peroxide, Sodium Nitroprusside, and Menadione

The adaptive responses of the two yeasts Yarrowia lipolytica and Pichia pastoris to oxidative stress induced by the oxidants hydrogen peroxide (H2O2), sodium nitroprusside (SNP), and menadione (MD) have been studied. The ability of these compounds to inhibit the growth of the yeast cells under culture conditions was tested. The inhibitory concentrations of the compounds were evaluated. The cell viability, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, and the lipids oxidation have also been investigated when exponential-phase cells are exposed to stress conditions. It was demonstrated that H2O2, SNP, and MD at 50%-inhibitory concentration affect the viability of both yeasts, probably by inhibiting the GAPDH and by causing other cell damages (lipid peroxidation), clearly augmented in the treated exponential-phase cells of Y. lipolytica and P. pastoris. On the other hand, enzymes involved in antioxidant defence systems such as catalase, glutathione peroxidase, and superoxide dismutase simultaneously significantly induced in the treated cells. The results showed that Y. lipolytica cells were more tolerant than P. pastoris cells to the presence of H2O2 and more sensitive in the presence of SNP and MD in the culture medium. Induction of these antioxidant enzymes with low doses of oxidants by pretreatment of yeast cells allowed them to tolerate higher doses of the compounds. Our data indicated that the increase of the cell viability agreed with the decrease of the lipid peroxidation and the increase of the GAPDH activity found after oxidative stress in pretreated cells.