4-hydroxynonenal inhibits glutathione peroxidase: protection by glutathione

4-Hydroxy-2,3- trans-nonenal, a lipid peroxidation product, inhibits glutathione peroxidase in a concentration-dependent manner. The concentration providing 50% inhibition is 0.12 mM. This inhibition can be almost completely (89%) prevented by 1 mM glutathione added to the incubation mixture 30 min before 4-hydroxy-2,3- trans-nonenal or 2,3- trans-nonenal, but not by other thiol-containing antioxidants such as 0.5 mM dithiothreitol or β-mercaptoethanol. Again the addition of 1 mM glutathione, and not of 0.5 mM dithiothreitol or β-mercaptoethanol, to the enzyme 30 min after incubation with 4-hydroxy-2,3- trans-nonenal restores activity to the same extent as does the preincubation with GSH. In view of the known reactivity of 4-hydroxy-2,3- trans-nonenal with lysine residues and the reversibility of the inhibition, the involvement of a lysine residue in GSH binding to glutathione peroxidase is proposed. The potential relevance of the inhibition of glutathione peroxidase by 4-hydroxy-nonenal to oxidative tissue damage is discussed with particular emphasis on neurological disorders.