Oxidative stress response in yeast: purification and some properties of a membrane-bound glutathione peroxidase from Hansenula mrakii.

Glutathione peroxidase was purified from the total membrane fractions of a yeast, Hansenula mrakii IFO 0895. The purified enzyme gave a single protein band with a molecular mass of 28 kDa on SDS-PAGE. The enzyme showed activity to various lipid hydroperoxides and their methyl esters. The enzyme was also active toward phosphatidylcholine hydroperoxide and cholesterol hydroperoxide. Since the enzyme was not active on hydrogen peroxide, the enzyme was thought to be a kind of glutathione S-transferase, although the purified enzyme did not show the glutathione-conjugating activity with electrophilic compounds such as 1-chloro-2,4-dinitrobenzene and o-dinitrobenzene, which are used as the substrate of glutathione S-transferase in yeast. The glutathione peroxidase in H. mrakii was then suggested to be a novel type of glutathione peroxidase in substrate specificity and intracellular localization, being different from those of other sources purified so far.