The Role of Saccharomyces cerevisiae NAD(H) Kinase Pos5p on the Defense of Oxidative Stress

Abstract:

In Saccharomyces cerevisiae, mitochondria NAD(H) kinase Pos5p has significant function. Absence of POS5 gene leads to antioxidative dysfunction. In order to realize the mechanism of anti-oxidative function of Pos5p and its relation to the conversion of coenzyme NAD(H) to NADP(H), we compared the growth phenotypes of wild-type BY4742, POS5 gene deletion mutant pos5Δ and pos5Δ containing POS5-YEplac195 plasmid (pos5Δ/POS5-YEp) under exposure to different kinds of oxidative reagents, and assayed their intracellular coenzyme concentration by the high performance liquid chromatography (HPLC). The results showed that only the pos5Δ had obvious growth defect under all of the three oxidative reagents, that is, superoxide anion generation reagent menadione (VK3), hydrogen peroxide (H2O2) and GSH consumption reagent diethyl maleate (DEM), while the tested anti-oxidative gene deletion mutants only had growth defect under their corresponding oxidative stress. In the normal growth condition, NADPH content of pos5Δ reduced, while that of pos5Δ/POS5-YEp increased, indicating that Pos5p play an important role on the supply of NADPH. Under the exposure to VK3, H2O2 and DEM, the NADP(H) concentration of BY4742, pos5Δ and pos5Δ/POS5-YEp all reduced, with the ratio of NADP(H) to NAD(H) in pos5Δ decreased most obviously. The research indicated that under different kinds of oxidative stress, Pos5p could exert NAD(H) kinase activity effectively to supply NADP(H) and thus had an important antioxidative defense funtion.