PURIFICATION AND CHARACTERIZATION OF GLUTATHIONE-PEROXIDASE FROM HUMAN BLOOD-PLATELETS - AGE-RELATED-CHANGES IN THE ENZYME

Platelet glutathione peroxidase (GPx) is known to play a pivotal role in controlling the level of lipid hydroperoxides, especially those res ulting from the 12-lipoxygenase activity. GPx was purified from the ce ll cytosol by more than 700-fold using an exchange chromatography, FPL P, gel filtration and covalent fixation. Isoelectric focusing revealed a peak activity at pH 5.1. The molecular mass of the enzyme was found between 90 and 100 kDa by gel filtration, and was approximating at 23 kDa by SDS-PAGE. A polyclonal antibody raised against commercial bovi ne erythrocyte GPx recognized the human platelet enzyme. It is conclud ed that human platelet GPx is likely a homotetramer of 92 kDa as descr ibed for most other sources. We have also found that the decreased pla telet GPx activity observed in platelets from elderly people is associ ated with a lower content of the immunoreactive enzyme.